tjp˙052
TJP-xml.cls
January 5, 2004
9:23
529
J Physiol 554.2 pp 529–541
Ovine feto-placental metabolism
J. W. Ward, F. B. P. Wooding and A. L. Fowden
Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
Fetal growth depends on the transplacental nutrient supply, which, in turn, is determined
partially by the consumption and production of nutrients by the uteroplacental tissues. In
fetal sheep, the rates of growth and umbilical glucose uptake decline coincidently towards
term in parallel with the normal prepartum rise in plasma cortisol. While cortisol is known
to reduce growth in fetal sheep, its effects on the uteroplacental handling and delivery of
nutrients remain unknown. Hence, this study, quantified the rates of umbilical uptake and
uteroplacental consumption of nutrients in preterm fetuses infused with cortisol for 5 days to
mimic the prepartum cortisol surge. Umbilical uptakes of glucose and lactate, but not oxygen,
were significantly lower in cortisol- than saline-infused fetuses, irrespective of whether values
were expressed as absolute or weight-specific rates. The rate of uteroplacental consumption
of glucose, but not oxygen, was significantly higher in cortisol- than saline-infused animals.
Absolute rates of uteroplacental lactate production were lower in cortisol-infused animals. When
all data were combined, fetal plasma cortisol levels were positively correlated to uteroplacental
glucose consumption and inversely related to umbilical glucose uptake. Cortisol treatment had
no apparent effect on placental mRNA expression for the glucose transporters, GLUT-1 and
GLUT-3. The results demonstrate that cortisol is physiological regulator of uteroplacental
metabolism and nutrient delivery to the sheep fetus. These observations have important
implications for fetal growth both in late gestation and during adverse intrauterine conditions,
which raise fetal cortisol levels earlier in gestation.
(Received 5 September 2003; accepted after revision 30 October 2003; first published online 31 October 2003)
Corresponding author A. L. Fowden: Department of Physiology, University of Cambridge, Downing Street, Cambridge
CB2 3EG, UK. Email: alf1000@cam.ac.uk
In all species studied to date, the major source of nutrients
for the fetus is transplacental transfer from the mother
with little, if any, endogenous nutrient production during
normal nutritional conditions (Battaglia, 1986). For
major oxidative substrates, such as glucose, transplacental
transfer depends on facilitated diffusion, which, in turn,
is determined by the transplacental glucose concentration
gradient and the availability of carrier proteins, the glucose
transporters (GLUTs). The amount of nutrient delivered
to the fetus is also affected by the metabolic activity of
the placenta itself. Ovine uteroplacental tissues have a
10-fold higher metabolic rate than the fetus, and consume
50% or more of the glucose taken up from the uterine
circulation before it reaches the fetus (Simmons et al. 1979;
Carver & Hay, 1995). These tissues also produce nutrients
such as lactate and certain amino acids, which are released
preferentially into the umbilical circulation for fetal use
during late gestation (Sparks et al. 1983; Carter et al. 1991;
Bell & Ehrhardt, 1998). However, the factors regulating
uteroplacental nutrient production and the partitioning
C The Physiological Society 2003
of nutrients between the fetal and uteroplacental tissues in
pregnant sheep remain unknown.
As the fetus grows throughout gestation, its increased
demand for nutrients is met by increasing the placental
supply of glucose by widening the transplacental glucose
concentration gradient and increasing GLUT expression
in the placenta (Molina et al. 1991; Ehrhardt & Bell, 1997).
However, in the last few days before birth, the growth rate
of the fetus declines and the umbilical uptake of glucose
falls by about 40% (Fowden et al. 1996; 1998b). These
changes closely parallel the final prepartum escalation
in the fetal plasma cortisol concentration (Fowden et al.
1998a). Indeed, glucocorticoids are known to decrease the
growth rate of the sheep fetus and to suppress placental
GLUT expression in humans and mice (Fowden et al.
1996; Derks et al. 1997; Hahn et al. 1999; Jensen et al.
2002). Yet, little is known about the direct effects of
fetal cortisol on the glucose supply to the fetus or on
the consumption and production of nutrients by the
uteroplacental tissues during late gestation. Hence, the
DOI: 10.1113/jphysiol.2003.054577
tjp˙052
TJP-xml.cls
January 5, 2004
530
9:23
J. W. Ward and others
aim of this study was to quantify the effects of cortisol on
the uteroplacental consumption, production and supply
of nutrients in chronically catheterized pregnant ewes,
with particular reference to the expression of the placental
glucose transporters, GLUT-1 and GLUT-3.
Methods
Animals
A total of 16 Welsh Mountain ewes of known gestational
age were used. All the ewes were housed in individual pens
and fed concentrates (100 g twice a day; Sheep Nuts #6; H &
C Beart Ltd, Kings Lynn, UK) and hay ad libitum. Food but
not water was withheld for 18–24 h before surgery. Normal
feeding regimes were restored within 24 h of surgery. All
procedures were carried out under UK Animals (Scientific
Procedures) Act, 1986.
Surgical procedures
Between 117 and 119 days of gestation (term 145 ± 2 days),
anaesthesia was induced by bolus injection of thiopentone
sodium (20 mg kg−1 ; Intraval Sodium; Rhone Mérieux,
Dublin, Ireland) and, after intubation, was maintained
with halothane (1.5–2.0% halothane in 50 : 50 O2 /N2 O;
Halothane Vet, Merial Animal Health Ltd, Harlow, UK).
Catheters were inserted into the umbilical vein, fetal dorsal
aorta and caudal vena cava via the tarsal veins, and into
the uterine ovarian vein and the maternal aorta via a
femoral artery using the surgical techniques previously
described (Comline & Silver, 1972). Antibiotics were given
intravenously into the fetus (100 mg ampicillin, Penbritin;
SmithKline Beecham Animal Health, Surrey, UK) at the
end of surgery and intramuscularly to the mother on the
day of surgery and for 3 days there after (9–12 mg i.m.
Depocillin; Mycofarm, Cambridge, UK).
Experimental procedures
Blood samples of 2 ml were taken daily throughout
the experimental period from the catheterized fetuses to
monitor fetal wellbeing, and to determine plasma cortisol.
After at least 6 days of postoperative recovery, fetuses
were assigned to one of two experimental groups. One
group of eight fetuses was infused for 5 days with cortisol
(1–3 mg kg−1 day−1 Efcortisol in 0.9% w/v NaCl, 2.4 ml
day−1 ). The dose of cortisol was increased incrementally
over the 5 days to mimic the normal prepartum cortisol
surge and reached a maximum of 3 mg kg−1 day−1 for
the final 24 h. The remaining eight fetuses were infused
J Physiol 554.2 pp 529–541
for 5 days with saline (0.9% NaCl, 2.4 ml day−1 ) to act as
age-matched controls.
Blood samples (2.5 ml) were taken simultaneously from
the fetal artey, umbilical vein, uterine vein and maternal
artery before commencement of the metabolic study on the
final day of infusion. Metabolite uptakes were measured
using the Fick principle and steady-state infusion of
antipyrine to determine umbilical and uterine blood flows
(Meschia et al. 1966). Antipyrine (2.8–4.1 mg min−1 kg−1
in sterile 0.9% saline) was infused at a rate of 0.145 ml
min−1 into a fetal vein catheter after an initial priming dose
of 3–4 ml. After approximately 2 h when steady state had
been established, four sets of blood samples (2.5 ml) were
drawn simultaneously from the fetal umbilical vein, fetal
artery, maternal artery and maternal vein. Blood samples
were drawn at 20 min intervals (120, 140, 160 and 180 min,
respectively).
At the conclusion of the experiments (128–130 days), all
fetuses were delivered by Caesarian section under terminal
anaesthesia (sodium pentobarbitone 200 mg kg−1 i.v.).
The position of all catheters was verified at delivery
and the fetus and placenta were weighed. Placentomes
representative of the general population in each animal
were frozen in liquid nitrogen.
Biochemical analyses
The simultaneous blood samples were analysed
immediately for blood pH, gas tension, packed cell
volume (PCV) and O2 content (0.5 ml) using standard
Radiometer (Radiometer, Copenhagen, Denmark) and
Hemoximeter equipment (ABL 330 Radiometer) that had
been calibrated with ovine blood (Owens et al. 1987).
Fetal and maternal lactate concentrations were measured
using a YSI 2300 Stat Plus (Yellow Springs Instruments,
Farnborough, UK). The remainder of the blood samples
(2 ml) were added to chilled tubes containing EDTA for
subsequent analyses. An aliquot (0.5 ml) of the chilled
EDTA-treated blood was immediately deproteinized with
zinc sulphate (0.3 m) and barium hydroxide (0.3 m) and
the supernatant used for determination of antipyrine and
total concentrations of blood glucose. The remaining
EDTA sample was centrifuged at 4◦ C and the plasma
stored at –20◦ C for later use in hormone analysis.
Plasma cortisol concentrations were measured using a
radioimmunoassay validated for use with ovine plasma
(Robinson et al. 1983). The interassay coefficient of
variation (%CV) was 7.3%. The concentration of
deproteinized whole blood glucose was determined
enzymatically with glucose oxidase (Sigma, UK) using
a spectrophotometer (Unicam Helios α, Cambridge,
C The Physiological Society 2003
tjp˙052
TJP-xml.cls
January 5, 2004
9:23
J Physiol 554.2 pp 529–541
Effects of cortisol on feto-placental metabolism
UK). The interassay %CV was 4.4%. Fetal plasma
insulin was measured using a commercially available
double antibody 125 I radioimmunoassay (RIA) using
human insulin as standard (Pharmacia Insulin RIA 100,
Pharmacia and Upjohn Diagnostics, Milton Keynes, UK).
The interassay %CV was 6.2%. Plasma catecholamines
concentrations were determined by high pressure liquid
chromatography using electrochemical detection (Silver
et al. 1987). The limits of sensitivity of the method were
70 pg ml−1 for adrenaline and 50 pg ml−1 for
noradrenaline.
Glucose transporter abundance
GLUT-1 and GLUT-3 mRNA expression was measured
using in situ hybridization (ISH) on frozen placentome
sections from eight study animals (matched by treatment
and sex of the fetus). The GLUT-1 and GLUT-3 sense
and antisense oligonucleotide probes (45 mer) were based
on a specific region of the ovine GLUT-1 and GLUT-3
cDNA sequence as isolated, cloned and sequenced
by Currie et al. (1997). Probes used in the current
study were synthesized by ‘The Microchemical Facility’
at the Babraham Institute, and were packaged as
1 µg µl−1 antisense and sense oligonucleotides
in diethylpyrocarbonate-treated water (DEPC). The
oligonucleotide probe sequence for GLUT-1 was: CTGC
TGAGCG TCATCTTCAT CCCGCCCTG TTGCAGTGCA
TCCTG. The oligonucleotide probe sequence for GLUT3 was: TCTTCTGCGG ACTCTGCACA GGATTCGTGC
CTATGTACAT TGGAG.
Frozen sections (6–8 µm) of placentomes were thaw
mounted onto poly-l-lysine-coated slides, fixed in 4%
(w/v) paraformaldehyde in PBS at 4◦ C for 5 min, rinsed in
PBS, dehydrated in an ethanol series and stored at 4◦ C in
95% alcohol. The slides were air-dried before incubation
with labelled probes. The oligonucleotide probes were endlabelled with (α-35 S)dATP (N.E.N Research Products, UK)
using terminal transferase (15–20 000 U ml−1 , Pharmacia,
UK), to catalyse the repetitive transfer of mononucleotide
units from the deoxynucleoside triphosphate to the 3 -OH
terminus. A small sample was counted on a β counter
to assess specific activity. Approximately 3 × 105 d.p.m.
of the probe in 100 µl hybridization buffer (50% (v/v)
formamide, 10% (w/v) dextran sulphate, 5 × Denhardts
(Sigma), 25 mm sodium phosphate (pH 7.0), 1 mm sodium
polyadenylic acid, 4 × SSC, 200 µg ml−1 salmon sperm
DNA), were added to each section. Hybridizations were
performed at 42◦ C for 16 h, and sections were then washed
for 2 × 1 h at room temperature and 1 h at 55◦ C in 1 ×
SSC containing 0.2% (w/v) sodium thiosulphate, followed
C The Physiological Society 2003
531
by a 5 min rinse in 1 × SSC and dehydration in an ethanol
series.
After air-drying the slides were placed in an
autoradiography cassette along with a sheet of X-ray
film (Kodac BioMax, Kodac, UK). The film was allowed
to develop for 5 days, after which it was removed and
developed in a imaging system (Xograft compact × 4,
Tetbury, Gloustershire, UK). X-ray image transfer was
undertaken using an adjustable illuminator and a camera
attached to compatible software (MCID.M4 Version 3.0;
Imagine Research Inc., Canada). This produced digital
images of the X-rays that were then evaluated using
integrated optical density (IOD) analysis software (Leica
QWIN Version 1.0, Cambridge, UK).
Measurements of IOD were made using a selection
frame that measured GLUT-1 and GLUT-3 mRNA density
relative to an adjacent reference area, which contained
no tissue. Non-specific binding (NSB) was measured
as IOD relative to reference background using sense
oligonucleotide-probed tissue on the same X-ray film.
Values for NSB were subtracted from the antisense
measurements to give the final IOD for GLUT abundance.
At least five final IOD measurements were made on
different areas of each probed section of tissue. A total of six
sections from each placentome were probed and quantified
for GLUT-1 and GLUT-3. Placentomes from four different
animals in each treatment group were analysed for GLUT
expression.
Calculations
All calculations were made using equations derived for
steady-state kinetics. Umbilical and uterine blood flow
was measured using the antipyrine steady-state diffusion
technique (Meschia et al. 1966) and calculated using the
following equations:
Umbilical blood flow (ml min−1 ) = infusion rate of
antipyrine (mg min−1 )/umbilical arterio
−venous concentration difference in blood
antipyrine (mg ml−1 )
(1)
Uterine blood flow (ml min−1 ) = infusion rate of
antipyrine (mg min−1 )/uterine venous–arterial
concentration difference in blood
antipyrine (mg ml−1 )
(2)
tjp˙052
TJP-xml.cls
January 5, 2004
9:23
532
J. W. Ward and others
J Physiol 554.2 pp 529–541
Table 1. Mean (± s.e.m.) values of fetal arterial concentrations of plasma cortisol insulin, noradrenaline and adrenaline on the day
of the metabolic study and of the morphometric measurements of the saline- (n = 8) and cortisol-infused (n = 8) fetuses at delivery
at the end of the metabolic study
Saline infused
Cortisol infused
Hormone concentrations
Cortisol (ng
Insulin (µU ml−1 )
Noradrenaline (pg ml−1 )
Adrenaline (pg ml−1 )
15.7 ± 1.2
7.0 ± 0.7
514 ± 105
126 ± 12
61.7 ± 5.3∗
5.7 ± 1.6
583 ± 174
163 ± 21
Morphometric measurements
Fetal weight (g)
Total placentome weight (g)
Total placentome number
Average placentome weight (g)
Fetal : placental wt ratio (g fetus (g placenta)−1 )
3033 ± 146
332 ± 29
72 ± 4
4.8 ± 0.6
9.5 ± 0.7
2968 ± 88
309 ± 20
72 ± 6
4.6 ± 0.5
9.8 ± 0.6
∗ Significantly
ml−1 )
different from the value in the saline-infused fetuses (P < 0.01, t test).
Table 2. Mean (± s.e.m.) values of pH, P O2 , P CO2 , haemoglobin (Hb) and percentage saturation of the haemoglobin in fetal and
maternal blood and of arterial concentrations of glucose and lactate in fetal and maternal plasma before (Day 0) and on the 5th day
(Day 5) of infusion of either saline (n = 8) or cortisol (n = 8) into the fetus
Fetus
Mother
Day 0
Day 5
Day 0
Day 5
pH
Saline
Cortisol
7.35 ± 0.01
7.35 ± 0.01
7.36 ± 0.01
7.36 ± 0.01
7.51 ± 0.01
7.51 ± 0.01
7.51 ± 0.01
7.48 ± 0.01
P O2 (mmHg)
Saline
Cortisol
22.0 ± 1.7
21.0 ± 0.7
19.0 ± 0.9
20.0 ± 1.0
97.0 ± 1.2
93.0 ± 1.8
95.0 ± 1.1
98.0 ± 2.4
P CO2 (mmHg)
Saline
Cortisol
53 ± 2.5
52 ± 0.7
52 ± 1.3
52 ± 0.8
33.0 ± 2.0
32.0 ± 0.5
34.0 ± 1.1
34.0 ± 0.8
Hb (g dl−1 )
Saline
Cortisol
9.5 ± 0.6
9.1 ± 0.2
9.9 ± 0.6
9.0 ± 0.7
10.4 ± 0.6
9.3 ± 0.4
9.6 ± 0.7
8.7 ± 0.4
% sat Hb
Saline
Cortisol
62.0 ± 3.3
57.0 ± 1.5
58.0 ± 2.8
57.0 ± 3.2
94.0 ± 0.8
96.0 ± 1.2
94.0 ± 1.0
97.0 ± 1.2
Plasma glucose (mmol l−1 )
Saline
Cortisol
0.85 ± 0.06
0.90 ± 0.07
0.94 ± 0.06
1.18 ± 0.08∗†
3.38 ± 0.15
3.43 ± 0.11
3.70 ± 0.13
3.41 ± 0.09
Plasma lactate (mmol l−1 )
Saline
Cortisol
1.30 ± 0.15
1.28 ± 0.16
1.36 ± 0.16
1.43 ± 0.16
0.40 ± 0.06
0.40 ± 0.08
0.52 ± 0.09
0.39 ± 0.07
∗ Significant
increase during treatment (P < 0.01, paired t test).† Significantly different from value in saline-infused animals (P < 0.01,
t test).
Net umbilical uptake of substrate (µmol min−1 ;
Net uterine output of substrate (µmol min−1 )
calculated using the Fick principle) = umbilical
= uterine blood flow (ml min−1 ) × uterine
blood flow (ml min−1 ) × umbilical venous
venous−arterial blood substrate
−arterial blood substrate concentration
concentration difference (µmol l−1 )
−1
difference (µmol l )
(5)
(3)
Net uterine uptake of substrate (µmol min−1 )
= uterine blood flow (ml min−1 ) × uterine arterio
(µmol min−1 ) = uterine substrate uptake (µmol
−venous blood substrate
concentration difference (µmol l−1 )
Net uteroplacental substrate consumption
(4)
min−1 )−umbilical substrate uptake (µmol l−1 ) (6)
C The Physiological Society 2003
tjp˙052
TJP-xml.cls
January 5, 2004
J Physiol 554.2 pp 529–541
9:23
Effects of cortisol on feto-placental metabolism
533
Table 3. Mean (±s.e.m.) values of umbilical and uterine blood flow, fetal and maternal arterial metabolite concentrations, the
absolute rates of umbilical and uterine uptakes or outputs of substrates and of the absolute rates of uteroplacental consumption or
production of substrates in animals in which the fetus was infused with either saline (n = 8) or cortisol (n = 8) for 5 days before the
measurements were made
Saline infused
Cortisol infused
P
Umbilical blood flow (ml min−1 )
Uterine blood flow (ml min−1 )
619 ± 33
1344 ± 75
691 ± 46
1546 ± 135
n.s.
n.s.
Glucose
Umbilical venous blood glucose (mmol l−1 )
Fetal arterial blood glucose (mmol l−1 )
Maternal arterial blood glucose (mmol l−1 )
Uterine venous blood glucose (mmol l−1 )
Umbilical glucose uptake (µmol min−1 )
Uterine glucose uptake (µmol min−1 )
Uteroplacental glucose consumption (µmol min−1 )
1.09 ± 0.05
0.93 ± 0.04
2.69 ± 0.13
2.55 ± 0.14
99.1 ± 5.9
177.3 ± 8.6
78.3 ± 10.5
1.28 ± 0.09
1.17 ± 0.09
2.77 ± 0.13
2.63 ± 0.13
72.9 ± 4.6
207.4 ± 26.4
134.5 ± 24.3
n.s.
0.024
n.s.
n.s.
0.003
n.s.
0.050
Lactate
Umbilical venous blood lactate (mmol l−1 )
Fetal arterial blood lactate (mmol l−1 )
Maternal arterial blood lactate (mmol 1−1 )
Uterine venous blood lactate (mmol l−1 )
Umbilical lactate uptake (µmol min−1 )
Uterine lactate output (µmol min−1 )
Uteroplacental lactate production (µmol min−1 )
1.29 ± 0.13
1.21 ± 0.13
0.49 ± 0.10
0.56 ± 0.09
49.1 ± 2.2
41.1 ± 4.0
90.2 ± 4.8
1.36 ± 0.15
1.31 ± 0.12
0.39 ± 0.08
0.44 ± 0.11
37.9 ± 3.8
34.1 ± 4.1
72.0 ± 6.3
n.s.
n.s.
n.s.
n.s.
0.022
n.s.
0.037
Oxygen
Umbilical venous blood oxygen content (mmol l−1 )
Fetal arterial oxygen content (mmol l−1 )
Maternal arterial oxygen content (mmol l−1 )
Uterine venous blood oxygen content (mmol l−1 )
Umbilical oxygen uptake (µmol min−1 )
Uterine oxygen uptake (µmol min−1 )
Uteroplacental oxygen consumption (µmol min−1 )
4.77 ± 0.19
3.41 ± 0.27
5.59 ± 0.32
3.00 ± 0.21
841 ± 31
1602 ± 97
794 ± 80
4.84 ± 0.31
3.30 ± 0.15
5.25 ± 0.41
2.89 ± 0.27
951 ± 54
1632 ± 169
692 ± 164
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
P = probability using unpaired Student’s t test. n.s. = not significant, P > 0.05.
Net uteroplacental substrate production (µmol min−1 )
(µmol min−1 ) ÷ net uteroplacental
= uterine substrate output (µmol min−1 )
+ umbilical substrate uptake (µmol l−1 )
% Distribution to fetus = [umbilical uptake
(7)
The percentage distributions of the net uterine uptake or
uteroplacental production of substrate between fetal and
either uteroplacental or maternal tissues were calculated
as follows:
For glucose and oxygen:
% Distribution to fetus = [umbilical uptake(µmol
min−1 ) ÷ uterine uptake (µmol min−1 )] × 100 (8)
production(µmol min−1 )] × 100
(10)
%Distribution to mother = [uterine uptake
(µmol min−1 ) ÷ net uteroplacental production
(µmol min−1 )] × 100
(11)
The sum of the percentage distribution to the fetal and
either the uteroplacental or maternal tissues is therefore
100%.
Statistical analyses
% Distribution to uteroplacental tissues
= [net uteroplacental consumption (µmol min−1 )
÷ uterine uptake (µmol min−1 )] × 100
For lactate:
C The Physiological Society 2003
(9)
Data were analysed using Microsoft Excel (Microsoft
Corp., Seattle, USA) and SigmaStat (v2.0 SPSS, Chicago,
USA). Results are presented as mean ± standard error
of the mean (s.e.m.) throughout. Groups were compared
using unpaired Student’s t test if parametric distributions
applied. Mann–Whitney rank sum tests were used for
TJP-xml.cls
January 5, 2004
9:23
534
J. W. Ward and others
non-parametric distributions. For all analyses, statistical
significance was accepted when P < 0.05.
Results
Plasma hormone levels and morphometric
measurements
Cortisol infusion for 5 days increased fetal cortisol
levels to values that were similar to those seen close
to term (Fowden et al. 1998a). On the 5th day of
infusion, the mean plasma cortisol concentration was
significantly higher in the cortisol-infused fetuses than
in the saline-infused controls (P < 0.001; Table 1). The
corresponding maternal concentrations of plasma cortisol
in the saline- and cortisol-infused animals were 15.3 ±
4.7 ng ml−1 (n = 7) and 14.7 ± 4.2 ng ml−1
(n = 8), respectively. Fetal arterial concentrations
of plasma insulin, noradrenaline and adrenaline were
measured on the day of the metabolic study and were
not significantly different between treatments (Table 1).
There were no significant differences in body weight,
total placental weight, average placentome weight, number
of placentomes or in the fetal-to-placental weight ratio
between cortisol- and saline-infused fetuses (Table 1, P >
0.05 all cases).
Metabolite concentrations, and acid–base
and blood gas status
Cortisol infusion had no effect on the arterial pH,
P O2 , P CO2 , haemoglobin concentration, or percentage O2
A
GLUCOSE UPTAKE
LACTATE UPTAKE
*
†
(i)
25
20
15
10
5
0
400
-1
-1
Oxygen (µmol min kg )
-1
-1
Lactate (µmol min kg )
15
12
9
6
3
0
Saline
Saline
GLUCOSE
CONSUMPTION
Cortisol
Saline
(iii)
3000
400
300
200
100
0
-1
-1
-1
Lactate (µmol min kg )
350
500
300
250
200
150
100
50
0
Cortisol
Cortisol
OXYGEN
CONSUMPTION
(ii)
600
Saline
100
LACTATE
PRODUCTION
‡
(i)
200
2500
-1
B
300
0
Cortisol
Oxygen (µmol min kg )
-1
-1
Glucose (µmol min kg )
30
saturation in either fetal or maternal blood (Table 2). Mean
values of these variables did not change with cortisol or
saline infusion and were similar in the two groups on
the 5th day of treatment (Table 2). There were also no
significant changes in fetal and maternal concentrations of
plasma lactate during treatment in either group (Table 2).
In contrast, fetal arterial concentrations of plasma glucose
rose in response to infusion of cortisol but not saline
(Table 2): mean values were therefore significantly higher
in cortisol- than saline-treated fetuses on the 5th day
of infusion (Table 2). Maternal arterial concentrations
of plasma glucose were unaffected by treatment in both
groups of animals (Table 2). Hence, the transplacental
gradient in plasma glucose concentration was significantly
less in animals treated with cortisol (2.26 ± 0.09 mmol l−1 ,
n = 8) than those receiving saline (2.74 ± 0.13 mmol l−1 ,
n = 8, P < 0.02). There were no significant differences in
the fetal or maternal metabolite concentrations, acid–base
status or in blood gas tensions between cortisol- and salineinfused animals before treatment began on Day 0 (Table 2).
The transplacental plasma glucose concentration gradient
was also similar in the cortisol- (2.68 ± 0.13 mmol l−1 ,
n = 8) and saline-infused animals (2.58 ± 0.14 mmol l−1 ,
n = 8) before treatment began.
During the metabolic study on the 5th day of infusion,
fetal, but not maternal, arterial concentrations of blood
glucose were significantly higher in cortisol- than salineinfused animals (Table 3). There were no significant
differences in the fetal or maternal concentrations of blood
lactate or in blood O2 content between the two treatment
groups during the metabolic study (Table 3).
(iii)
18
35
J Physiol 554.2 pp 529–541
OXYGEN UPTAKE
(ii)
40
-1
-1
Glucose (µmol min kg )
tjp˙052
2000
1500
1000
500
0
Saline
Cortisol
Saline
Cortisol
Figure 1. Rates of (A) umbilical uptake
and (B) uteroplacental consumption or
production of glucose (i) lactate (ii) and
oxygen (iii)
Rates were expressed as weight-specific
values (µmol min−1 kg−1 ) per kg fetal weight
(A) or kg placenta (defined as total
placentome mass) (B). Fetuses were infused
with either saline (n = 8) or cortisol (n = 8).
Significant differences are: ∗ P < 0.02; † P <
0.05; ‡ P < 0.039 (Student’s unpaired t test).
C The Physiological Society 2003
January 5, 2004
J Physiol 554.2 pp 529–541
9:23
Effects of cortisol on feto-placental metabolism
Metabolic rates
On the 5th day of treatment, substrate uptakes from the
uterine circulation and substrate delivery to the umbilical
circulation were calculated using the Fick principle and
the respective uterine and umbilical blood flows (see
eqns (3)–(5)). Cortisol infusion into the fetus had no
apparent effect on either the uterine or umbilical blood
flow: mean values for each of these flows were similar in
the saline- and cortisol-infused animals (Table 3).
Umbilical substrate uptake. Cortisol infusion appeared
to have no effect on the umbilical uptake of O2 ; mean rates
were similar in the saline- and cortisol-infused fetuses,
irrespective of whether values were expressed in absolute
terms (Table 3) or per kilogram fetal body weight (Fig. 1A).
In contrast, the rates of umbilical uptake of glucose and
lactate were significantly lower in cortisol- than salineinfused fetuses both as absolute values (Table 3) and
when calculated on a weight-specific basis (Fig. 1A). When
all the data were combined irrespective of treatment,
there was a significant inverse correlation between the
fetal plasma cortisol concentration at the time of the
metabolic study and the rate of umbilical uptake of
glucose (Fig. 2A), but not lactate (r = –0.419, n = 16,
P > 0.05).
535
(Fig. 1B(ii), P > 0.05). When all data were combined,
there was a significant positive correlation between
the fetal plasma cortisol concentration at the time of the
metabolic study and the rate of uteroplacental glucose
consumption (Fig. 2B). No significant correlations were
observed between fetal plasma cortisol and the rates of O2
consumption and lactate production by the uteroplacental
tissues expressed either as absolute or weight-specific
values (P > 0.05, all cases)
Nutrient partitioning
The distributions of the glucose and O2 taken up from the
uterine circulation between the fetal and uteroplacental
A
50
45
Umbilical Glucose
Uptake (µmo l min -1 kg -1 )
TJP-xml.cls
40
35
30
25
20
15
Uterine substrate uptake. The mean rates of uptake of
O2 and glucose from the uterine circulation were not
significantly different in the saline- and cortisol-infused
animals (Table 3). There was a significant output of lactate
from the uteroplacental tissues into the uterine circulation
in both groups of animals, which did not differ in absolute
rate with treatment (Table 3).
Uteroplacental substrate consumption and production.
The rates of uteroplacental consumption of O2 and glucose
were calculated as the difference between the uterine
and umbilical uptakes (eqn (6), Methods), while the
uteroplacental production of lactate was estimated as
the sum of the rates of umbilical lactate uptake and
uteroplacental lactate output into the uterine circulation
(eqn (5), Methods). The uteroplacental consumption
of glucose, but not O2 , was significantly higher in
cortisol- than saline-infused animals, both in absolute
terms (Table 3) and when expressed per kilogram
placenta (total placentome weight, Fig. 1B). Absolute rates
of uteroplacental lactate production were significantly
less in cortisol- than saline-infused animals (Table 3).
However, when production was expressed per kilogram
placental weight, this difference was no longer significant
C The Physiological Society 2003
10
10
20
30
40
50 60 70 80
100
-1
Cortisol Concentration (ng ml )
B
Uteroplacental Glucose
Consumption (µmo l min -1 kg -1 )
tjp˙052
800
700
600
500
400
300
200
100
0
10
20
30
40
50 60 70 80
100
-1
Cortisol Concentration (ng ml )
Figure 2. Relationships between the fetal plasma cortisol
concentration (ng ml−1 ) and either umbilical glucose uptake (A)
or uteroplacental glucose consumption (B)
Uptake expressed in µmol min−1 (kg fetus)−1 ; y = –0.162x + 35.374,
n = 16, r = 0.52, P < 0.037); consumption expressed in µmol min−1
(kg placenta)−1 ; y = 4.232x + 174.520, n = 16,
r = 0.60, P < 0.014). Fetuses were infused with either saline ( ✉, n =
8) or cortisol ( ❡, n = 8).
TJP-xml.cls
January 5, 2004
9:23
J. W. Ward and others
% Distribution
GLUCOSE
OXYGEN
J Physiol 554.2 pp 529–541
LACTATE
100
100
80
80
60
60
*
40
40
20
0
20
Saline
Cortisol
Saline
Cortisol
Saline
Cortisol
% Distribution
536
0
Figure 3. The effects of cortisol on the distribution of nutrients
The mean (± S.E.M.) percentage distribution of the uterine uptake of glucose and oxygen between fetal (black
columns) and uteroplacental tissues (grey columns) and of uteroplacental lactate production between fetal (black
columns) and maternal tissues (grey columns) in saline- (n = 8) and cortisol-infused fetuses (n = 8). ∗ P < 0.008,
compared to saline-infused controls (Student’s unpaired t test). 100% = total uterine uptake or uteroplacental
production, irrespective of absolute value.
tissues in the cortisol- and saline-infused animals and
are shown in Fig. 3 together with the partitioning of
uteroplacental lactate production between the fetus and
mother in the two treatment groups (eqns (8)–(11),
Methods). The percentage distribution of uterine glucose
uptake to the fetus was significantly less in cortisol- than
saline-infused animals (Fig. 3). There were no significant
differences in the partitioning of uterine O2 uptake or
uteroplacental lactate production between the two groups
of animals (Fig. 3).
Placental GLUT-1 and GLUT-3 mRNA expression
A
GLUT-1
Cortisol
GLUT-3
Saline
Cortisol
ANTISENSE
SENSE
Saline
Using in situ hybridization and X-ray densitometry,
GLUT-1 and GLUT-3 mRNA were detected readily in
all placentomes studied, and were evenly distributed
throughout the fetal and maternal tissue in the
placentomes (Fig. 4A). Cortisol had no apparent effect
on the placental abundance of GLUT-1 or GLUT-3
mRNA; mean values of GLUT-1 and GLUT-3 mRNA
abundance in the saline-infused fetuses were not
significantly different from the corresponding values
in the cortisol-infused animals (P > 0.05 all cases,
Fig. 4B).
B
0.5
GLUT-1
GLUT-3
Discussion
0.4
IOD Units
tjp˙052
0.3
0.2
0.1
0.0
Saline
Cortisol
Saline
Cortisol
Figure 4. The effect of cortisol on placental GLUT expression
In situ hybridization analysis of GLUT-1 and GLUT-3 mRNA expression
shown as typical sections through placentomes from cortisol- and
saline-infused fetuses visualized with the sense and antisense
oligionucleotide probes (A) and mean (± S.E.M.) values of integrated
optical density (IOD) units of placentome sections from saline- (n = 4)
and cortisol-infused fetuses (n = 4) (B).
The results demonstrate that uteroplacental metabolism
is regulated by cortisol in pregnant sheep during late
gestation. Cortisol infusion reduced the delivery of
glucose and lactate from the uteroplacental tissues to
the umbilical circulation both in absolute terms and
when expressed per kilogram fetal body weight. It had
no effect on the uteroplacental delivery of oxygen.
The fall in umbilical glucose uptake in the cortisolinfused fetuses was accompanied by an elevated fetal
glucose concentration, a lower transplacental glucose
concentration gradient and an increased uteroplacental
consumption of glucose compared to the saline-infused
controls, but was not associated with any apparent changes
C The Physiological Society 2003
tjp˙052
TJP-xml.cls
January 5, 2004
J Physiol 554.2 pp 529–541
9:23
Effects of cortisol on feto-placental metabolism
in placental GLUT abundance. Uteroplacental glucose
consumption was significantly increased in the cortisolinfused fetuses, both in absolute terms and when expressed
per kilogram placental weight. In contrast, uteroplacental
lactate production was reduced in absolute terms, but
not when expressed per gram placental weight. Cortisol
infusion had no effect on the rate of uteroplacental
consumption and uterine uptake of O2 . Nor did it
affect the uterine uptake and output of glucose and
lactate, respectively. Cortisol infusion into the fetus
therefore appears to alter both uteroplacental substrate
utilization and uteroplacental delivery of nutrients to
the fetus. Indeed, the reciprocal correlations observed
between fetal plasma cortisol and the uteroplacental
consumption and fetal delivery of glucose suggest that
cortisol may be a physiological regulator of uteroplacental
glucose handling over the normal range of cortisol
concentrations found in the sheep fetus during late
gestation.
Glucose metabolism
The reduced rate of umbilical glucose uptake measured
after 5 days of fetal cortisol infusion in the present
study is the first unequivocal demonstration that cortisol
regulates the uteroplacental delivery of glucose to the
fetus. Previous studies have shown no effect of shortterm (4 h) infusion of cortisol on umbilical glucose
uptake by fetal sheep at 124 days of gestation (Milley,
1996). More long-term treatment (24 h) of sheep fetuses
with the synthetic glucocorticoid dexamethasone provided
indirect evidence of a glucocorticoid-mediated reduction
in placental glucose delivery by using the modified
Widdas equation to estimate umbilical glucose uptake
from the fetal and maternal glucose concentrations (see
Widdas, 1952; Hay et al. 1990). The rates of umbilical
glucose uptake measured in the saline-infused animals
in the current study were similar to those reported
previously for fetuses at the same stage of gestation
in this and other laboratories (Owens et al. 1987; Hay
et al. 1990; Jensen et al. 1999). In addition, the rates of
umbilical glucose uptake in the cortisol-infused fetuses
were within the range of values observed in older control
fetuses with high endogenous cortisol levels close to
term (Fowden et al. 1998b). Umbilical glucose uptake
therefore appears to be reduced at high concentrations
of cortisol, whether of exogenous or endogenous
origin.
The mechanisms by which cortisol reduced the
umbilical glucose uptake remain unclear, but may
have involved changes in the transplacental glucose
C The Physiological Society 2003
537
concentration gradient, the placental glucose transfer
capacity and in the rate of uteroplacental glucose
consumption. Previous studies of fetal glucocorticoid
overexposure induced by maternal administration of
synthetic glucocorticoids have shown a decrease in the
transplacental glucose concentration gradient which is
associated with increases in both fetal and maternal
glycaemia during late gestation (Barbera et al. 1997;
Bennett et al. 1999). In the present study, the transplacental
glucose concentration gradient was reduced by 15–20% in
response to fetal cortisol infusion, primarily as a result of
a rise in the fetal arterial plasma glucose concentration.
This suggests that, in the current study, the fall in the
transplacental gradient is predominantly of fetal origin,
and may arise either from decreased glucose utilization
and/or a rise in glucose production by the fetus. In late
gestation, the rise in endogenous cortisol level is not
accompanied by any change in the rate of fetal glucose
utilization (Fowden et al. 1998b). Cortisol also had no
effect on the fetal concentration of insulin, a major
factor regulating glucose utilization by the fetus (Fowden
et al. 1998b). The rise in fetal glycaemia in response
to cortisol is therefore unlikely to be due to a fall in
the fetal glucose utilization. An increase in fetal glucose
production is a more likely explanation as cortisol is known
to increase the glucogenic capacity of the fetus, and has
been shown to activate hepatic gluconeogenesis in sheep
fetuses close to term (Townsend et al. 1989; Fowden et al.
1993). An increase in endogenous glucose production
also occurs in normal fetuses with high cortisol levels
close to term (Fowden et al. 1998b). Since catecholamines
are known to stimulate hepatic glucose production in
fetal sheep (Apatu & Barnes, 1991), the tendency for
higher total catecholamine concentrations during cortisol
infusion may favour endogenous glucose production in
these fetuses.
Whatever the cause of the rise in fetal glucose level,
the increase in fetal glycaemia relative to maternal values
will decrease the driving force for facilitated diffusion of
glucose across the placenta. Using the modified Widdas
equation (Widdas, 1952; Hay et al. 1990), this decrease
in transplacental glucose concentration gradient would
account for about half the reduction in the rate of
umbilical glucose uptake observed during cortisol infusion
in the present study. However, the modified Widdas
equation predicts an umbilical glucose uptake of about
28–30 µmol min−1 kg−1 for the glucose levels observed
in the current cohort of cortisol-infused animals, which
is higher than the value actually observed (24 µmol
min−1 kg−1 , Fig. 1Ai). This suggests that other factors
such as changes in the placental glucose transfer capacity
tjp˙052
TJP-xml.cls
538
January 5, 2004
9:23
J. W. Ward and others
or uteroplacental glucose consumption contribute to the
reduced umbilical glucose uptake observed during cortisol
infusion.
The capacity for placental glucose transfer at specific
glucose concentration gradients is determined by the
placental area for exchange, the number of transporters
and by the rate of placental glucose consumption. All
these factors contribute to the increase in placental
glucose transfer capacity that occurs with increasing
gestational age in pregnant sheep (Molina et al. 1991).
Previous studies have also shown down-regulation of
GLUT-1 expression in response to fetal hypoglycaemia
in ovine placentomes and suppression of both GLUT-1
and GLUT-3 by glucocorticoids in human and mouse
placentae (Das et al. 1998; Hahn et al. 1999). In the
current study, there were no apparent differences in
the abundance or localization of GLUT-1 and GLUT3 mRNA in placentomes following cortisol infusion. In
situ hybridization is widely accepted as a sufficiently
robust and accurate method for quantifying gene
expression and has the added advantage of establishing
the cellular localization of the specific mRNAs (Gadd
et al. 2000; Mitchell et al. 2002). Although further
studies are required to determine whether cortisol affects
expression of GLUT proteins in ovine placentomes, the
current observations suggest that changes in transporter
abundance are unlikely to make a major contribution
to the cortisol-induced decrease in umbilical glucose
uptake.
The rate of uteroplacental glucose consumption was
80% higher in cortisol- than saline-infused animals. Since
there was no significant difference in uterine glucose
uptake with treatment, the fractional distribution of
the maternally derived glucose between the fetal and
uteroplacental tissues was altered by cortisol infusion, with
significantly more of the uterine glucose uptake being
used by the uteroplacental tissues in the cortisol-infused
animals. In normal animals, experimental manipulation
of the fetal and maternal glucose levels has shown that
uteroplacental glucose consumption is a function of the
fetal glucose concentration, and is virtually independent
of the maternal glucose concentration (Hay et al. 1990).
The rise in the fetal glucose level observed in response to
cortisol infusion would therefore be expected to increase
uteroplacental glucose consumption (Hay, 1995). Using
the equation relating uteroplacental glucose consumption
to fetal glycaemia derived by Hay et al. (1990), the current
cortisol-induced rise in fetal glycaemia would be predicted
to increase uteroplacental glucose consumption by
25–50 µmol min−1 , which is within the range of values
actually observed (Table 3). The rise in uteroplacental
J Physiol 554.2 pp 529–541
glucose consumption may therefore be the consequence,
rather than the cause, of the reduced umbilical glucose
uptake.
Lactate metabolism
Much less is known about the regulation of the production
and transfer of lactate by the ovine uteroplacental tissues.
Lactate production by these tissues normally increases
with increasing gestational age towards term (Aldoretta
& Hay, 1999). This ontogenic change is accompanied
by a switch in the distribution of uteroplacental lactate
production, from delivery preferentially into the uterine
circulation at midgestation, to output predominantly
into the umbilical circulation close to term (Sparks
et al. 1983). The current rate of uteroplacental lactate
production and the distribution between the maternal
and fetal tissues in the saline-infused animals were similar
to those reported previously for sheep fetuses at the
same stage of gestation (Sparks et al. 1982). Cortisol
infusion decreased both the rates of umbilical lactate
uptake and absolute uteroplacental lactate production,
but not the weight-specific rate of uteroplacental lactate
production. There was also no change in the fetal lactate
concentration, or in the distribution of uteroplacental
lactate production between the fetal and maternal
tissues.
In normal animals, the uteroplacental tissues provide
about one-third of the lactate used by the fetus (Sparks
et al. 1982). Since fetal lactate levels were unaffected by
cortisol infusion, lactate production by the fetal tissues may
rise to compensate for the decreased uteroplacental supply.
This suggestion is consistent with the rise in fetal glucose
levels observed during cortisol infusion, as previous
studies have shown that fetal lactate production is directly
related to glucose availability in the fetal circulation
(Sparks et al. 1983). In normal well-fed animals,
uteroplacental lactate production increases directly with
the rate of uteroplacental glucose consumption (Aldoretta
& Hay, 1999). Hence, increased rather than decreased
uteroplacental lactate production would have been
expected during cortisol infusion. Previous studies have
shown that fetal insulin-like growth factor-I (IGF-I)
infusion decreases umbilical uptake and uteroplacental
production of lactate in association with a tendency for
increased uteroplacental glucose consumption (Harding
et al. 1994; Jensen et al. 1999). Although fetal cortisol
infusion has no effect on fetal IGF-I concentrations
(Li et al. 1996), it does induce tissue-specific changes
in IGF-I gene expression (Li et al. 1996; 2002).
Cortisol may therefore reduce placental lactate production
C The Physiological Society 2003
tjp˙052
TJP-xml.cls
January 5, 2004
J Physiol 554.2 pp 529–541
9:23
Effects of cortisol on feto-placental metabolism
through up-regulation of placental IGF-I expression,
independently of its effects on uteroplacental glucose
consumption.
539
occur in the placenta when fetal cortisol levels are raised
(Challis et al. 2000).
Conclusions
Oxygen metabolism
Cortisol infusion had no effects on the umbilical uptake,
uterine uptake or uteroplacental consumption of O2 . Nor
did it affect the distribution of uterine oxygen uptake
between the uteroplacental and fetal tissues. All rates of
uteroplacental consumption, uterine and umbilical uptake
of O2 measured in the current study were within the range
of values reported previously for normal sheep fetuses at
the same stage of gestation in this and other laboratories
(Harding et al. 1994; Jensen et al. 1999). Since O2 uptake
is flow mediated, and dependent on the diffusion distance
across the placenta, the current observations suggest that
cortisol had little effect on the vascular architecture or
diffusion distance within the placentomes. In contrast,
the absence of cortisol-induced changes in fetal and
uteroplacental O2 consumption despite the concomitant
alterations in carbohydrate metabolism indicates that
cortisol may alter relative use of substrates for oxidative
metabolism by both the fetal and uteroplacental tissues.
In the fetus, less placentally derived carbohydrate is
available for oxidation and, hence, oxidation must be
maintained either by other carbohydrate sources (e.g.
glucogenesis in the fetal liver and kidney), or by use
of non-carbohydrate substrates such as amino acids or
lipid. This will reduce the availability of substrates for
tissue accretion and may explain, in part, the decreased
growth rate observed in cortisol-infused fetuses (Fowden
et al. 1996). In the uteroplacental tissues, more glucose
is available during cortisol infusion, although the fate
of these extra glucose molecules remains unknown.
In normal animals, increasing the glucose supply to
the uteroplacental tissues increases the oxidative use of
glucose, but even at high glucose availability, only 34%
of the uteroplacental glucose consumption is oxidized
by these tissues (Aldoretta & Hay, 1999). A significant
amount of the glucose taken up by the uteroplacental
tissues is therefore used to synthesize other molecules
such as lactate, fructose, proteins, lipids and amino
acids (Fowden, 1993). In addition, since uteroplacental
O2 consumption was unaffected by cortisol, increased
oxidative use of glucose will increase the availability of the
alternate oxidative substrates, e.g. lipids and amino acids.
Taken together, these changes in uteroplacental substrate
availability are likely to have major effects on processes
such as tissue differentiation and hormone synthesis that
C The Physiological Society 2003
The current results indicate that cortisol affects many
aspects of uteroplacental metabolism. It influences the
consumption, production, fetal delivery and oxidative
use of glucose and lactate. However, the extent to which
its actions are direct, or mediated via changes in fetal
metabolism remain unclear. Cortisol appeared to have
little direct effect on the placental glucose transfer capacity,
as there were no apparent changes in mRNA abundance
for the placental glucose transporters GLUT-1 and GLUT3. The effects of cortisol on the rate of umbilical uptake
and uteroplacental consumption of glucose appeared to
be indirect, and mediated through the rise in the fetal,
relative to maternal glucose levels. The primary effect of
cortisol may therefore have been to activate fetal glucose
production (Townsend et al. 1989; Fowden et al. 1993;
1998b). In turn, the increase in fetal glycaemia reduced
the transplacental glucose concentration gradient and
increased uteroplacental glucose consumption. Hence, less
glucose was transferred from the uteroplacental tissues
to the fetus. These changes in fetal, relative to maternal
glycaemia, and in uteroplacental glucose handling may
have led to the observed alterations in feto-placental lactate
metabolism. Further studies measuring the fetal rates
of utilization and production of glucose during cortisol
infusion are required before the mechanisms by which
cortisol acts on feto-placental metabolism can be fully
elucidated.
References
Aldoretta PW & Hay WW (1999). Effect of glucose supply on
ovine uteroplacental glucose metabolism. Am J Physiol 277
(4), R947–R958.
Apatu RS & Barnes RJ (1991). Release of glucose from the liver
of fetal and postnatal sheep by portal vein infusion of
catecholamines or glucagon. J Physiol 436, 449–468.
Barbera A, Wilkening RB, Teng C, Battaglia FC & Meschia G
(1997). Metabolic alterations in the fetal heaptic and
umbilical circulations during glucocorticoid-induced
parturition in sheep. Ped Res 41, 242–248.
Battaglia FC (1986). An Introduction to Fetal Physiology.
Academic Press, Orlando.
Bell AW & Ehrhardt RA (1998). Placental Regulation of
Nutrient Partitioning During Pregnancy. In: Nutrition &
Reproduction, eds. Bray GA, Hansel W and Ryan DH,
pp. 229–254. Louisiana. State University Press, Baton Rouge.
tjp˙052
TJP-xml.cls
540
January 5, 2004
9:23
J. W. Ward and others
Bennett L, Kozuma S, Mcgarrigle HHG & Hanson MA (1999).
Temporal changes in fetal cardiovascular, behavioural,
metabolic and endocrine responses to maternally
administered dexamethasone in the late gestation fetal sheep.
Br J Obstr Gyn 106, 331–339.
Carter BS, Moores RR & Battaglia FC (1991). Placental
transport and fetal and placental metabolism of amino acids.
J Nutr Biochem 2, 4–13.
Carver TD & Hay WW (1995). Uteroplacental carbon substrate
metabolism and O2 consumption after long-term
hypoglycemia in pregnant sheep. Am J Physiol 269,
E299–E308.
Challis JRG, Matthew SG, Gibb W & Lye SJ (2000). Endocrine
and paracrine regulation of birth at term and preterm.
Endocr Rev 21, 514–550.
Comline RS & Silver M (1972). The composition of foetal and
maternal blood during parturition in the ewe. J Physiol 222,
233–256.
Currie MJ, Bassett NS & Gluckman PD (1997). Ovine glucose
transporter-1 and -3: cDNA partial sequences and
developmental gene expression in the placenta. Placenta 18,
393–401.
Das UG, Sadiq HF, Soares MJ, Hay WW & Devaskar SU
(1998). Time-dependent physiological regulation of rodent
and ovine placental glucose transporter (GLUT-1) protein.
Am J Physiol 274, R339–R347.
Derks JB, Giussani DA, Jenkins SL, Wentworth RA, Visser GH,
Padbury JF & Nathanielsz PW (1997). A comparative study
of cardiovascular, endocrine and behavioural effects of
betamethasone and dexamethasone administration to fetal
sheep. J Physiol 499, 217–226.
Ehrhardt RA & Bell AW (1997). Developmental increases in
glucose transporter concentration in the sheep placenta. Am
J Physiol 273, R1132–R1141.
Fowden AL (1993). Fetal metabolism and energy balance. In:
Textbook of Fetal Physiology, ed. Harding R and Thorburn
GD, pp. 70–82. Oxford Medical Publications, Melbourne.
Fowden AL, Li J & Forhead AJ (1998a). Glucocorticoids and
the preparation for life after birth: are there long-term
consequences of the life insurance? Proc Nutr Soc 57,
113–122.
Fowden AL, Mijovic J & Silver M (1993). The effects of cortisol
on hepatic and renal gluconeogenic enzyme activities in the
sheep fetus during late gestation. J Endo 137, 213–222.
Fowden AL, Mundy L & Silver M (1998b). Developmental
regulation of glucogenesis in the sheep fetus during late
gestation. J Physiol 508, 937–947.
Fowden AL, Szemere J, Hughes P, Gilmour RS & Forhead AJ
(1996). The effects of cortisol on the growth rate of the sheep
fetus during late gestation. J Endo 151, 97–105.
Gadd TS, Osgersby JC & Wathes DC (2000). Regulation of
insulin-like growth factor binding protein-6 expression in
the reproductive tract throughout the estrous cycle and
during the development of the placenta in the ewe. Biol
Reprod 67, 1756–1762.
J Physiol 554.2 pp 529–541
Hahn T, Barth S, Graf R, Engelmann M, Beslagic D, Reul JM,
Holsboer F, Dohr G & Desoye G (1999). Placental glucose
transporter expression is regulated by glucocorticoids. J Clin
Endo Metab 84, 1445–1452.
Harding JE, Liu L, Evans PC & Gluckman PD (1994).
Insulin-like growth factor 1 alters feto-placental protein and
carbohydrate metabolism in fetal sheep. Endo 134,
1509–1514.
Hay WW (1995). Regulation of placental metabolism by
glucose supply. Reprod Fert Dev 7, 365–375.
Hay WW, Molina RA, DiGiacomo JE & Meschia G (1990).
Model of placental glucose consumption and glucose
transfer. Am J Physiol 258, R569–R577.
Jensen EC, Gallaher BW, Breier BH & Harding JE (2002). The
effect of a chronic maternal cortisol infusion on the
late-gestation fetal sheep. J Endo 174, 27–36.
Jensen EC, Harding JE, Bauer MK & Gluckman PD (1999).
Metabolic effects of IGF-I in the growth retarded fetal sheep.
J Endo 161, 485–494.
Li J, Forhead AJ, Dauncey MJ, Gilmour RS & Fowden AL
(2002). Control of growth hormone receptor and
insulin-like growth factor-I expression by cortisol in ovine
fetal skeletal muscle. J Physiol 541, 581–589.
Li J, Owens JA, Owens PC, Saunders JC, Fowden AL & Gilmour
RS (1996). The ontogeny of hepatic growth hormone
receptor and insulin-like growth factor I gene expression in
the sheep fetus during late gestation: developmental
regulation by cortisol. Endo 137, 1650–1657.
Meschia G, Cotter JR, Makowski EL & Barron DH (1966).
Simultaneous measurement of uterine and umbilical blood
flows and oxygen uptakes. Quart J Exp Physiol 52,
1–18.
Milley JR (1996). Fetal substrate uptake during increased ovine
fetal cortisol concentration. Am J Physiol 271,
E186–E191.
Mitchell SE, Robinson JJ, King ME, McKelvey WAC & Williams
LM (2002). Interleukin 8 in the cervix of non-pregnant ewes.
Reprod 124, 409–416.
Molina R, Meschia G, Battagli FC & Hay WW (1991).
Gestational maturation of placental glucose transfer
capacity in sheep. Am J Physiol 261,
R697–R704.
Owens JA, Falconer J & Robinson JS (1987). Effect of restriction
of placental growth on oxygen delivery to and consumption
by the pregnant uterus and fetus. J Dev Physiol 9, 137–150.
Robinson PM, Comline RS, Fowden AL & Silver M (1983).
Adrenal cortex of fetal lamb: changes after hypophysectomy
and effects of Synacthen on cytoarchitecture and secretory
activity. Quart J Exp Physiol 68, 15–27.
Silver M, Fowden AL, Knox J, Ousey JC, Franco R & Rossdale
PD (1987). Sympathoadrenal and other responses to
hypoglycaemia in the young foal. J Reprod Fert Suppl 35,
607–614.
Simmons MA, Battaglia FC & Meschia G (1979). Placental
transfer of glucose. J Dev Physiol 1, 227–243.
C The Physiological Society 2003
tjp˙052
TJP-xml.cls
January 5, 2004
J Physiol 554.2 pp 529–541
9:23
Effects of cortisol on feto-placental metabolism
Sparks JW, Hay WW, Bonds D, Meschia G & Battaglia FC
(1982). Simultaneous measurements of lactate turnover rate
and umbilical lactate uptake in the fetal lamb. J Clin Invest
70, 179–192.
Sparks JW, Hay WW, Meschia G & Battaglia FC (1983).
Partition of maternal nutrients to the placenta and fetus in
the sheep. Eur J Obstr Gynec Reprod Biol 14,
331–340.
Townsend SF, Rudolph CD, Wood CE & Rudolph AM (1989).
Perinatal onset of hepatic gluconeogenesis in the lamb. J Dev
Physiol 12, 329–335.
C The Physiological Society 2003
541
Widdas WF (1952). Inability of diffusion to account for
placental glucose transfer in the sheep and consideration of
the kinetics of a possible carrier transfer. J Physiol 118, 23–39.
Acknowledgements
The authors wish to acknowledge Mr Paul Hughes for his
technical assistance during surgery and Mrs Sue Nicholls for
the routine care of the animals used in this study. This work was
supported by the Avrith Research studentship (J.W.W.).