NUTRITION RESEARCH, Vol. 5, pp. 395-403, 1985
027]-5~7/85 $3.00 + .00 Printed in the USA.
Copyright (c) 1985 Pergamon Press Ltd. All rights reserved.
INCREASED
CONCENTRATION
ESSENTIAL
Harald
OF V A S O P R E S S I N
FATTY ACID-DEFICIENT
S H a n s e n a) , B e n n y
IN P L A S M A OF
RATS
J e n s e n a) and J ~ r g e n W a r b e r g b)
a) B i o c h e m i c a l L a b o r a t o r y ,
U n i v e r s i t e t s p a r k e n 2, DK tute of M e d i c a l P h y s i o l o g y
B l e g d a m s v e j 3c, DK - 2200,
Royal D a n i s h S c h o o l of Pharmacy,
2100 C o p e n h a g e n @, and b) InstiC, U n i v e r s i t y of C o p e n h a g e n ,
C o p e n h a g e n N, D e n m a r k .
ABSTRACT
The e f f e c t of e s s e n t i a l fatty a c i d d e f i c i e n c y (EFA-D) on
the p l a s m a c o n c e n t r a t i o n of a r g i n i n e - v a s o p r e s s i n
(AVP) and
the u r i n a r y AVP e x c r e t i o n w a s i n v e s t i g a t e d .
W e a n l i n g rats
w e r e fed a f a t - f r e e diet (FF-rats).
C o n t r o l rats r e c e i v e d
the same diet in w h i c h 6% by wt. of s u c r o s e w a s r e p l a c e d by
a r a c h i s oil.
A f t e r 4-6 w e e k s of feeding, urine a n d p l a s m a
w e r e a n a l y s e d for AVP, o s m o l a l i t y , s o d i u m and p o t a s s i u m .
W h e n c o m p a r e d to c o n t r o l rats F F - r a t s h a d d e c r e a s e d u r i n e volume (6.0 • 1.6 mi/24 hr v e r s u s 11.7 • 3.2 m i / 2 4 hr), inc r e a s e d u r i n e o s m o l a l i t y (2409 • 691 m O s m / k g v e r s u s 1260 •
434 m O s m / k g ) , i n c r e a s e d u r i n a r y A V P e x c r e t i o n (5.52 • 1.62
ng/24 hr v e r s u s 2.19 • 1.20 n g / h r and i n c r e a s e d p l a s m a AVP
(2.55 • 0.45 p g / m l v e r s u s 1.95 • 0.25 pg/ml).
T h e r e was no
d i f f e r e n c e b e t w e e n the g r o u p s in p l a s m a o s m o l a l i t y .
The trie n e / t e t r a e n e r a t i o n w a s 0.78 + 0.15 (n = 12) in t o t a l k i d n e y
lipids of the FF-rats.
The t r i e n e / t e t r a e n e r a t i o was positively correlated with urinary AVP excretion.
It is c o n c l u d ed that F F - r a t s had e l e v a t e d p l a s m a A V P c o n c e n t r a t i o n and
d i s t u r b e d w a t e r balance, b o t h of w h i c h p r o b a b l y w e r e prov o k e d by an i n c r e a s e d t r a n s e p i d e r m a l w a t e r loss.
Key Words:
R e n a l fatty
- plasma electrolytes.
acids
- transepidermal
water
loss
INTRODUCTION
I n c r e a s e d t r a n s e p i d e r m a l w a t e r loss, i n c r e a s e d w a t e r c o n s u m p t i o n
and d e c r e a s e d urine o u t p u t are some of the w e l l k n o w n e f f e c t s of
e s s e n t i a l f a t t y a c i d d e f i c i e n c y (EFA-D) (1,2,3,4).
P r e v i o u s l y we
h a v e f o u n d t h a t E F A - D rats h a d an i n c r e a s e d u r i n a r y e x c r e t i o n of
i m m u n o r e a c t i v e A V P (5), a s y m p t o m w h i c h t o g e t h e r w i t h i n c r e a s e d
w a t e r c o n s u m p t i o n d e v e l o p e d r a t h e r e a r l y d u r i n g e x p e r i m e n t a l ind u c t i o n of E F A - D (6).
It has b e e n s u g g e s t e d that p r o p o r t i o n a l i t y
e x i s t s b e t w e e n u r i n a r y A V P e x c r e t i o n and p l a s m a A V P c o n c e n t r a t i o n
395
396
H.S. HANSENet al.
(7,8,9). ~However, renal e x c r e t i o n of e x o g e n o u s A V P has b e e n rep o r t e d to v a r y c o n s i d e r a b l y in rats (10), i n d i c a t i n g that c a u t i o n
s h o u l d be t a k e n w h e n r a t i o n a l i z i n g f r o m an o b s e r v e d d i f f e r e n c e in
u r i n a r y A V P e x c r e t i o n b e t w e e n two e x p e r i m e n t a l groups to a possible d i f f e r e n c e in t h e i r p l a s m a A V P c o n c e n t r a t i o n .
It was t h e r e fore the p u r p o s e of the p r e s e n t i n v e s t i g a t i o n to study w h e t h e r the
p r e v i o u s l y d e m o n s t r a t e d i n c r e a s e in u r i n a r y A V P e x c r e t i o n in EFAD rats (5,6) was a c c o m p a n i e d b y e l e v a t e d p l a s m a A V P levels.
The
d e g r e e of E F A - D in these rats has b e e n e v a l u a t e d b y the r a t i o o f
20:3(n-9) to 20:4(n-6) in total k i d n e y lipids.
A r a t i o b e l o w 0.4
has b e e n s u g g e s t e d to i n d i c a t e n o r m a l EFA status of the animal
(11).
MATERIAL
AND METHODS
A n i m a l s : T w e n t y four 2 1 - d a y s o l d m a l e M o l - W i s t a r rats (K. M ~ l l e g ~ r d - H a n s e n s A v l s l a b o r a t o r i u m A/S, L i l l e S k e n s v e d , Denmark) w e r e
d i v i d e d into t w o groups.
One group (FF-rats) r e c e i v e d a semis y n t h e t i c f a t - f r e e diet as d e s c r i b e d p r e v i o u s l y (6,12), the o t h e r
group (control rats) was r e a r e d on the f a t - f r e e d i e t in w h i c h
6% by wt. of the sucrose was r e p l a c e d by the same a m o u n t of arachis oil c o n t a i n i n g 40 wt.% linoleate.
The e x p e r i m e n t a l f e e d i n g
p e r i o d s t a r t e d in M a y and e n d e d in June.
The diet and w a t e r w e r e
s u p p l i e d ad l i b i t u m t h r o u g h o u t the e x p e r i m e n t .
The a n i m a l s were
h o u s e d in w i r e m e s h cages (2 a n i m a l s / c a g e ) u n d e r c o n t r o l l e d cond i t i o n s of t e m p e r a t u r e (23 • I C) and l i g h t i n g (lights on 06001800 hr).
The r e l a t i v e h u m i d i t y was b e t w e e n 40% and 50%.
After
4 w e e k s of f e e d i n g the rats w e r e t r a n s f e r r e d to m e t a b o l i c cages
w h e r e they w e r e k e p t i n d i v i d u a l l y for 24 hr w i t h free a c c e s s to
food a n d water.
The w a t e r i n t a k e was m e a s u r e d .
D u r i n g the 24
hr p e r i o d u r i n e w a s c o l l e c t e d in a p o l y e t h y l e n e t u b e p a c k e d in dry
ice, w h i c h e n s u r e d i m m e d i a t e f r e e z i n g of the u r i n e a f t e r voiding.
The u r i n e s a m p l e s w e r e s t o r e d at -20C u n t i l A V P d e t e r m i n a t i o n s
were performed.
F o l l o w i n g the m e t a b o l i c e x p e r i m e n t t h e rats w e r e r e t u r n e d to the
wire m e s h cages w h e r e they w e r e k e p t u n t i l d e c a p i t a t i o n w i t h i n
the f o l l o w i n g two weeks.
D e c a p i t a t i o n t o o k p l a c e b e t w e e n 10 and
11.00 hr and was p e r f o r m e d q u i c k l y a n d w i t h o u t b o d y c o m p r e s s i o n .
This p r o c e d u r e a i m e d to r e d u c e any e f f e c t of d i u r n a l v a r i a t i o n
in p l a s m a A V P c o n c e n t r a t i o n (13) and r e s t r a i n t - i n d u c e d s t i m u l a t i o n
of A V P r e l e a s e (14).
B l o o d was c o l l e c t e d in c h i l l e d glass tubes
c o n t a i n i n g h e p a r i n (170.000 U/g, L ~ v e n s K e m i s k e Fabrik, Ballerup,
D e n m a r k ) , final c o n c e n t r a t i o n 10 U/ml blood.
P l a s m a for o s m o l a l i ty d e t e r m i n a t i o n was k e p t at 4 C and a n a l y z e d w i t h i n 24 hr; w h i l e
p l a s m a for A V P d e t e r m i n a t i o n w a s s t o r e d at -20 C. E x c i s e d k i d n e y s
w e r e weighed, w r a p p e d in a l u m i n i u m foil, f r o z e n in p o w d e r e d dry
ice, a n d s t o r e d at -80 C u n t i l a n a l y z e d .
A V P - r a d i o i m m u n o a s s a y : Two d i f f e r e n t a s s a y s W i t h two d i f f e r e n t
a n t i s e r a were used. A v P - a s s a y I w h i c h was u s e d for a n a l y s i s of
u r i n e was i d e n t i c a l to t h a t p r e v i o u s l y d e s c r i b e d (5,6).
The
s e n s i t i v i t y of this a s s a y w a s 1.8 pg per tube.
The A V P a n t i s e rum w a s k i n d l y p r o v i d e d by Dr. J.D. C h r i s t e n s e n , B i o l o g i c a l Lab o r a t o r y , R o y a l D a n i s h S c h o o l of P h a r m a c y (15). A V P - a s s a y II
ESSENTIAL FATTY ACID DEFICIENCY
397
w h i c h was p e r f o r m e d a c c o r d i n g to Bie and W a r b e r g (16) had a
h i g h e r s e n s i t i v i t y (0.4 pg p e r tube) and was u s e d for d e t e c t i o n
of A V P in plasma.
P r i o r to m e a s u r e m e n t A V P w a s e x t r a c t e d from
p l a s m a u s i n g a c e t o n e and p e t r o l e u m e t h e r as p r e v i o u s l y d e s c r i b e d
(16).
The e f f i c i e n c y of the e x t r a c t i o n w a s 72%.
R e s u l t s are
not c o r r e c t e d for this recovery.
The a n t i s e r u m w h i c h was r a i s e d
in r a b b i t s i m m u n i z e d w i t h A V P c o v a l e n t l y c o u p l e d to p o r c i n e t h y r o globulin exhibited partial cross-reactivity with lysine-vasopressin, b u t d i d not c r o s s - r e a c t w i t h oxytocin.
U r i n e and p l a s m a o s m o l a l i t i e s were d e t e r m i n e d on a f r e e z i n g - p o i n t
o s m o m e t e r and u r i n e and p l a s m a s o d i u m a n d p o t a s s i u m c o n c e n t r a tions w e r e d e t e r m i n e d by f l a m e p h o t o m e t r y (model 343, I n s t r u m e n tation Laboratory).
L i p i d a n a l y s i s : E a c h k i d n e y was cut into small p i e c e s and homog e n i z e d in 20 vol c h l o r o f o r m / m e t h a n o l
(2:1, v/v) u s i n g an UltraT u r r a x h o m o g e n i z e r w i t h a No. 10 shaft.
The tube was kept on
ice a n d f l u s h e d w i t h n i t r o g e n d u r i n g the 60-sec h o m o g e n i z a t i o n .
The h o m o g e n a t e was f i l t e r e d and the r e s i d u e was r e h o m o g e n i z e d
w i t h 10 v o l c h l o r o f o r m / m e t h a n o l
(1:2, v/v) . The c o m b i n e d filt r a t e s w e r e e v a p o r a t e d u n d e r r e d u c e d p r e s s u r e at 25-30 C.
The
c r u d e lipids w e r e r e d i s s o l v e d in 5.0 ml c h l o r o f o r m .
M e t h y l esters of fatty acids w e r e p r e p a r e d by t r a n s e s t e r i f i c a t i o n w i t h
10% (w/w) h y d r o g e n c h l o r i d e in m e t h a n o l by h e a t i n g to 100 C for
1.5 hr.
A f t e r m e t h y l a t i o n , I ml w a t e r was a d d e d to the vials,
a n d the e s t e r s w e r e e x t r a c t e d w i t h 2 x 2 ml p e t r o l e u m ether.
The m e t h y l e s t e r e x t r a c t s w e r e a n a l y z e d in d u p l i c a t e by gas c h r o m a t o g r a p h y on a p a c k e d g l a s s c o l u m n (10% SP 2330 on 100/120 m e s h
C h r o m o s o r b W / A W (Supelco, B e l l e f o n t e , PA) in a 6 m m x 1.8 m column, t e m p e r a t u r e - p r o g r a m m e d f r o m 160 C to 210 C; P e r k i n E l m e r
3920 gas c h r o m a t o g r a p h w i t h a flame i o n i z a t i o n d e t e c t o r ) .
The
p e a k a r e a s w e r e q u a n t i t a t e d u s i n g a H e w l e t t - P a k c a r d 3 3 9 0 A recording i n t e g r a t o r .
The r e t e n t i o n times w e r e c o m p a r e d w i t h those
of s t a n d a r d s for t e n t a t i v e i d e n t i f i c a t i o n .
S t a t i s t i c a l a n a l y s e s w e r e done u s i n g
sults are p r e s e n t e d as m e a n • SD.
Student's
t-test.
The re-
RESULTS
The F F - r a t s e x c r e t e d a h i g h l y c o n c e n t r a t e d
of r e d u c e d w a t e r e x c r e t i o n (Table I).
urine
as a c o n s e q u e n c e
The F F - r a t s had a h i g h u r i n a r y A V P e x c r e t i o n , w h i c h was 2.5 times
t h a t of the controls.
The w a t e r c o n s u m p t i o n was the same in the
two g r o u p s w h e n e x p r e s s e d p e r animal.
A r o u g h e s t i m a t i o n of
e v a p o r a t i o n was m a d e by c a l c u l a t i n g the d i f f e r e n c e b e t w e e n w a t e r
intake and urine output.
This " e v a p o r a t i o n " was 17.1 • 4.9 mi/24 hr
in the F F - r a t s w h i c h is s i g n i f i c a n t l y d i f f e r e n t (p < 0.05) from
t h a t of the c o n t r o l rats, 12.6 • 2.9 m i / 2 4 hr.
The F F - r a t s
also h a d e l e v a t e d c o n c e n t r a t i o n of p l a s m a AVP, b e i n g 1 . 3 - f o l d that
of the c o n t r o l s (Table 2).
398
H.S. HANSEN et al.
TABLE
Water
Intake
and Urine
I
Parameters
after
4 Weeks
FF-rats
(n = 12)
Water
intake,
mi/24
hr
Urine
volume,
ml/24
hr
Sodium,
meq/l
Potassium,
meq/l
• 4.6 a
23.9
6.0
+- 1.6 b
11.7
• 3.2
-+ 53 b
1260
• 434
141
• 53 b
85
• 31
• 72 b
134
• 49
ng/24
FF-rats: Young
duce essential
rats raised on a fat-free diet
fatty acid-deficiency.
Values
n = 11
significantly
5.52
different
Parameters
•
b
from
TABLE
Plasma
control
Sodium,
meq/l
Potassium,
AVP,
mOsm/kg
rats
• 1.20
in o r d e r to ina r e m e a n s • SD.
(p < 0.05)
after
6 Weeks
of F e e d i n g
Control rats
(n = 12)
297.3
• 3.4
297.0
• 4.0
143.0
-+ 1.4
143.3
• 1.4
6.8
• 0.7
7.0
• 0.7
meq/1
pg/ml
2.19
2
FF-rats
(n = 11)
Osmolality,
• 4.8
230
AVP-excretion,
a)
b)
hr
Control rats
(n = 12)
23.1
2409
Osmolality, mOsm/kg
of F e e d i n g
2.55
• 0.45 a
1.95
• 0.25
F F - r a t s : y o u n g r a t s w e r e r a i s e d o n a f a t - f r e e d i e t in o r d e r to
induce essential fatty acid-deficiency.
V a l u e s are m e a n s • SD.
a)
significantly
different
from control
rats.
(p<0.05)
ESSENTIAL FATTY ACID DEFICIENCY
399
T h e r e w a s no d i f f e r e n c e in p l a s m a o s m o l a l i t y , n o r in s o d i u m a n d
potassium concentrations
in p l a s m a b e t w e e n t h e t w o g r o u p s . T h e r e
w a s no c l e a r c o r r e l a t i o n b e t w e e n p l a s m a A V P c o n c e n t r a t i o n a n d p l a s ma
o s m o l a l i t y w i t h i n a r a n g e of 289 to 302 m O s m / k g (data not
shown).
The FF-rats showed a statistically significant
(p < 0.05)
r e d u c t i o n of g r o w t h u s u a l l y s e e n in F F A - d e f i c i e n c y
(2); t h e b o d y
w e i g h t a f t e r six w e e k s of f e e d i n g t h e e x p e r i m e n t a l d i e t s
were
224 • 16 g f o r the F F - r a t s (n = 12), a n d 278 • 17 g f o r t h e c o n t r o l r a t s (n = 12).
A n a l y s i s of t o t a l k i d n e y f a t t y a c i d s r e v e a l e d a r e d u c t i o n in the
p e r c e n t a g e of l i n o l e a t e - d e r i v e d
f a t t y a c i d s a n d the a p p e a r a n c e of
5,8,11-icosatrienoic
a c i d ( T a b l e 3).
TABLE
3
Fatty Acid Composition
of T o t a l K i d n e y L i p i d s a f t e r
Fatty
acid
(Peak A r e a %)
6 W e e k s of F e e d i n g
FF-rats
(n = 12)
Control rats
(n = 12)
20.6
-+ 0.6
19.9
• 0.6
16:1
5.2
• 0.4
1.6
-+ 0.3
18:0
14.0
• 0.3
16.0
+- 0.5
18:1
24.1
-+ 0.9
15.7
• 1.5
2.3
-+ 0.4
7.9
-+ 0.2
10.3
-+ 1.0
16:0
18:2
20:3(n-9)
20:3(n-6)
n.d.
20:4(n-6)
13.4
-+ 1.4
22:3(n-9)
0.6
-+ 0.1
22:4(n-9)
or
24:0
2.9
22:4(n-6)
• 0.4
n.d.
n.d.*
1.0
+ 0.1
28.9
• 1.0
n.d
2.6
-+ 0.2
1.0
+- 0.4
24:1
3.0
-+ 0.4
3.1
+ 0.6
22:6(n-3)
0.8
• 0.1
0.9
-+ 0.1
20:3(n-9)/20:4(n-6)
0.78
+- 0 . 1 5
0
F F - r a t s : y o u n g r a t s w e r e r a i s e d o n a f a t - f r e e d i e t in o r d e r to
induce essential fatty acid-deficiency.
Values are peak area
%, m e a n • SD.
*)
n.d.
= not
detected
400
H.S. HANSEN et al.
The h i g h t r i e n e / t e t r a e n e r a t i o i n d i c a t e d a p r o n o u n c e d state of
E F A - d e f i c i e n c y in the FF-rats.
A p o s i t i v e c o r r e l a t i o n was found
b e t w e e n u r i n a r y A V P e x c r e t i o n and t r i e n e / t e t r a e n e r a t i o of t o t a l
k i d n e y l i p i d s in the FF-rats: y = 0.42 + 0.063x (r = 0.68;
p < 0.02), w h e r e y is the t e t r a e n e r a t i o and x is u r i n a r y A V P
e x c r e t i o n in rig/24 hr.
DISCUSSION
The F F - r a t s h a d s i g n i f i c a n t l y e l e v a t e d u r i n a r y A V P e x c r e t i o n as
w e l l as s i g n i f i c a n t l y e l e v a t e d p l a s m a A V P c o n c e n t r a t i o n .
The
v a l u e for p l a s m a A V P c o n c e n t r a t i o n in the c o n t r o l rats (Table 2)
is in good a g r e e m e n t w i t h those r e p o r t e d by o t h e r s (9,14,17,18).
The v a l u e for p l a s m a A V P c o n c e n t r a t i o n in the F F - r a t s , b e i n g
0.60 p g / m l h i g h e r t h a n the c o n t r o l s m a y fully e x p l a i n the diff e r e n c e in u r i n e o s m o l a l i t y b e t w e e n the two d i e t a r y groups. Bie
a n d W a r b e r g h a v e shown t h a t i n c r e m e n t s in p l a s m a A V P of less than
I p g / m l can i n d u c e p r o f o u n d a n t i d i u r e s i s in t r a i n e d dogs (19).
M o r e r e c e n t d a t a i n d i c a t e that an i n c r e a s e of as little as
0.23 p g / m l w i l l induce a n t i d i u r e s i s (20).
In the F F - r a t s u r i n a r y AVP e x c r e t i o n was i n c r e a s e d by a f a c t o r
2.5 w h i l e p l a s m a A V P c o n c e n t r a t i o n w a s i n c r e a s e d b y a f a c t o r 1.3,
only.
A l t h o u g h the u r i n e samples w e r e c o l l e c t e d two w e e k s before p l a s m a samples, this d i f f e r e n c e in time of s a m p l i n g cannot
e x p l a i n the d i f f e r e n t f a c t o r s found, i.e. 2.5 and 1.3.
Previously, we have f o u n d that w h e n y o u n g r a t s w e r e r e a r e d on a l i n o l e a t e d e f i c i e n t diet, t h e i r u r i n a r y A V P e x c r e t i o n b e g a n to rise already w i t h i n four w e e k s of f e e d i n g the d e f i c i e n t diet, r e a c h i n g a
c o n s t a n t level of ca. 4.8 m U / 2 4 hr (12.3 ng/24 hr) a f t e r approximately 8-12 w e e k s of f e e d i n g (5,6).
Thus, if urine samples had
b e e n c o l l e c t e d at the same time as t h e p l a s m a s a m p l e s we p r o b a b l y w o u l d h a v e found an e v e n h i g h e r u r i n a r y AVP e x c r e t i o n in the
FF-rats.
The c o n t r o l rats w h i c h w e r e fed an a d e q u a t e diet h a d a
u r i n a r y AVP e x c r e t i o n of ca. 2.2 ng/24 hr (Table I) in a g r e e m e n t
w i t h our p r e v i o u s r e s u l t s (5,6).
In o r d e r to e x c l u d e that the
d i f f e r e n c e in ratios, 2.5 in urine and 1.3 in plasma, was due to
the use of two d i f f e r e n t A V P - a s s a y s , the two m e t h o d s w e r e comp a r e d by m e a s u r i n g u r i n e AVP c o n c e n t r a t i o n s w i t h b o t h assays.
W h e n r e s u l t s f r o m A V P - a s s a y I w e r e p l o t t e d along the abscissa,
and t h o s e f r o m A V P - a s s a y II a l o n g the ordinate, the f o l l o w i n g reg r e s s i o n line w a s obtained: y = 30.6 + 0.58 x; n = 24; r = 0.951;
p < 0.001.
The i n t e r c e p t of the r e g r e s s i o n line w a s i n s i g n i f i c a n t l y d i f f e r e n t from zero i n d i c a t i n g the r e l i a b i l i t y of the two
a s s a y s in t e r m s of r e l a t i v e c o m p a r i s o n s b e t w e e n the A V P - v a l u e s
o b t a i n e d in the two g r o u p s of rats.
Thus, the d i f f e r e n c e in the
ratios, 1.3 in p l a s m a and 2.5 in urine, c o u l d p o s s i b l y i n d i c a t e
a h i g h e r renal c l e a r a n c e of A V P d u r i n g E F A - d e f i c i e n c y .
The p r e s e n t e x p e r i m e n t does not e x p l a i n the e l e v a t e d A V P c o n c e n t r a t i o n in the E F A - d e f i c i e n t rats.
Plasma AVP c o n c e n t r a t i o n in
the a d e q u a t e l y fed rat is r e g u l a t e d by s e v e r a l factors, e.g.
p l a s m a o s m o l a l i t y , b l o o d v o l u m e (17) and n o r e p i n e p h r i n e (18).
T h e r e was no d i f f e r e n c e in p l a s m a o s m o l a l i t y b e t w e e n the two
ESSENTIAL FATTY ACID DEFICIENCY
401
g r o u p s a l t h o u g h the E F A - d e f i c i e n t rats had e l e v a t e d p l a s m a AVP
concentrations.
F u r t h e r i n v e s t i g a t i o n s are n e e d e d b e f o r e an exp l a n a t i o n can be o f f e r e d for the e l e v a t e d p l a s m a AVP.
F a t t y a c i d a n a l y s i s of total k i d n e y lipids (Table 3) r e v e a l e d
in the F F - r a t s a h i g h t r i e n e / t e t r a e n e ratio, i n d i c a t i n g pronounced EFA-deficiency.
We o b s e r v e d t h a t rats h a v i n g a h i g h
t r i e n e / t e t r a e n e r a t i o n also h a d a h i g h u r i n a r y A V P e x c r e t i o n .
Thus i n c r e a s e d u r i n a r y A V P e x c r e t i o n in rats fed a f a t - f r e e diet
seems to be a s y m p t o m r e l a t e d to E F A - d e f i c i e n c y w h i c h can be
q u a n t i t a t i v e l y c o r r e l a t e d w i t h a n o t h e r E F A - d e f i c i e n c y symptom,
the i n c r e a s e d t r i e n e / t e t r a e n e ratio.
The " e v a p o r a t i o n " e s t i m a t e d as the d i f f e r e n c e b e t w e e n w a t e r intake a n d u r i n e o u t p u t w a s e l e v a t e d in the F F - r a t s as we have
seen p r e v i o u s l y (6,21).
However, this can be m a n i f e s t e d as an
i n c r e a s e d w a t e r c o n s u m p t i o n / d e c r e a s e d u r i n e o u t p u t (18), inc r e a s e d w a t e r c o n s u m p t i o n / u n c h a n g e d urine o u t p u t (6), or as in
the p r e s e n t e x p e r i m e n t u n c h a n g e d w a t e r c o n s u m p t i o n / d e c r e a s e d
u r i n e o u t p u t (Table I).
In all these e x p e r i m e n t s u r i n a r y A V P
e x c r e t i o n was s i g n i f i c a n t l y i n c r e a s e d (5,6) (Table I).
Variable
r e s u l t s on urine o u t p u t d u r i n g E F A - d e f i c i e n c y h a v e also b e e n
r e p o r t e d by o t h e r s (1,2,22).
The r e a s o n for this v a r i a b l e urine
r e s p o n s e is not o b v i o u s to us.
The i n c r e a s e d " e v a p o r a t i o n " is
p r o b a b l y due to i n c r e a s e d t r a n s e p i d e r m a l w a t e r loss, w h i c h could
be c a u s e d by a lack of l i n o l e i c a c i d in the c u t a n e o u s w a t e r barrier (23,24,25).
An i n c r e a s e d w a t e r loss o v e r the skin p r o b a b l y
r e s u l t s in s t i m u l a t i o n of w a t e r i n t a k e a n d / o r d e c r e a s e in renal w a t e r excretion.
In s u m m a r y this study shows that our p r e v i o u s o b s e r v a t i o n of inc r e a s e d u r i n a r y A V P e x c r e t i o n in E F A - d e f i c i e n t rats is accompanied with increased plasma AVP concentration.
The e l e v a t e d
p l a s m a A V P c o n c e n t r a t i o n seems to be the r e a s o n for the excretion of the v e r y c o n c e n t r a t e d u r i n e by these E F A - d e f i c i e n t rats.
F u r t h e r m o r e , in w e a n l i n g rats fed a f a t - f r e e d i e t for 4-6 w e e k s
the u r i n a r y AVP e x c r e t i o n seems to increase w i t h the d e g r e e of
E F A - d e f i c i e n c y as e s t i m a t e d f r o m the t r i e n e / t e t r a e n e r a t i o of
total k i d n e y lipids.
ACKNOWLEDGMENTS
Prof. E. A a e s - J ~ r g e n s e n and Dr. P. Bie are t h a n k e d for a d v i c e and
and c r i t i c i s m .
Jytte C h r i s t i a n s e n , Elsa L a r s e n and Inge Pedersen are t h a n k e d for s k i l l f u l t e c h n i c a l a s s i s t a n c e .
Vitamins
w e r e a gift from H o f f m a n La R o c h e and Co., Basel, S w i t z e r l a n d .
This w o r k has b e e n s u p p o r t e d by the D a n i s h Fat R e s e a r c h Foundation.
402
H,S, HANSENet a l
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