Experiment 4
Endocrine Physiology: PhysioEx of Metabolic Rate in Mice/Rats
S. Blanco | L. J. Cabural | M. K. A. Calimag | C. I. Cabornay
4Biology7
Summary
The Endocrine System controls a variety of processes within the body. An example of this is
through the release of thyroxine by the thyroid gland to regulate body temperature. In addition,
hormones present in the body such as estrogen and calcitonin also play an important role in
protection against certain diseases such as osteoporosis. The results of the first activity show that
injection with thyroxine in all three rats caused hyperthyroidism without goiter formation;
injection with TSH caused hyperthyroidism in normal and hypophysectomized rats with goiter
formation, and had no effect on the thyroidectomized rat; and finally, injection with PTU caused
hypothyroidism in all three rats, with the normal rat exhibiting goiter formation. The results of the
second activity show that since both of them yielded a negative T-score in the injection of estrogen,
it made the rat normal from an osteoporotic state while the injection of calcitonin made the rate
osteopenic from and osteoporotic state. Thus, both estrogen and calcitonin improved the bone
structure and can be, therefore, used in hormone-replacement therapy.
1 | INTRODUCTION
hormones bind to high-affinity receptors,
which can be found on the surface of the said
The
endocrine
system—the
other
target cell, the nucleus, or the cytosol. With
communication system in the body—is made
the formation of the hormone-receptor
up of endocrine glands that produce
complex, a biological action can be formed
hormones, chemical substances released into
through the signal-transduction cascades as
the bloodstream to guide processes such as
well as the alteration of the cellʼs gene
metabolism,
transcription.
growth,
and
sexual
Thyroidhormone receptors
development. Hormones are also involved in
exert their regulatory functions by acting as
regulating emotional life (Chawla, 2016).
both activators and repressers of gene
The blood then carries the secreted
hormones to the target cells.
expression (Horlein et al., 2002).
These
Endocrine Physiology: Metabolic Rate in Mice/Rats | 1
The endocrine system regulates its
is considered one of the most important
hormones through negative feedback, except
thyroid hormones. Understanding thyroxine
in very specific cases like childbirth.
is crucial to protecting your overall health.
Increases in hormone activity decrease the
The pituitary gland and hypothalamus both
production of that hormone. The immune
control the thyroid. When thyroid hormone
system and other factors contribute as control
levels drop too low, the hypothalamus
factors also, altogether maintaining constant
secretes TSH Releasing Hormone (TRH),
levels of hormones (Adrignola, 2005).
which alerts the pituitary to produce thyroid
The thyroidʼs main role in the
stimulating hormone (TSH). The thyroid
endocrine system is to regulate your
responds to this chain of events by producing
metabolism, which is your bodyʼs ability to
more hormones (Sargis, 2010).
break down food and convert it to energy.
Thyroid
stimulating
hormone
is
Food essentially fuels the body, and each of
produced and released into the bloodstream
our bodies uses that fuel at different rates.
by the pituitary gland. It controls production
This is why you often hear about some people
of the thyroid hormones, thyroxine and
having a “fast” metabolism and others having
triiodothyronine, by the thyroid gland by
a “slow” metabolism.
binding to receptors located on cells in the
The thyroid keeps your metabolism
thyroid
gland.
Thyroxine
and
under control through the action of thyroid
triiodothyronine are essential to maintaining
hormone, which it makes by extracting iodine
the bodyʼs metabolic rate, heart and digestive
from the blood and incorporating it into
functions, muscle control, brain development
thyroid hormones. Thyroid cells are unique in
and maintenance of bones.
that they are highly specialized to absorb and
Other hormones can also be found in
use iodine. Every other cell depends on the
the body such as estrogen and calcitonin
thyroid to manage its metabolism.
which plays essential roles in the woman’s
The thyroid gland is an important part
reproductive system and protection against
of the endocrine system, secreting a number
bone diseases. Estrogen, also known as sex
of hormones that affect everything from heart
hormones, is a vital hormone that is needed
health to metabolism. One of those hormones
for the reproductive system to function, and
is thyroxine, also known as T4. Because of
for the menstrual cycle to be regulated. This
the many functions that thyroxine impacts, it
hormone
usually
travels
through
the
Endocrine Physiology: Metabolic Rate in Mice/Rats | 2
bloodstream in fluids, interacts with cells in a
gas chamber. Meanwhile, the soda lime
variety of tissues in the body, and delivers a
found on the bottom of the gas chaber absorbs
message or instruction. Lastly, calcitonin is a
the CO2 released by the rat. Water levels in
physiologic endogenous inhibitor of bone
the manometer were also noted for any
reabsorption
osteoclast
variations as the time progresses. A T-
formation, osteoclast attachment, and bone
connecter knob was used as well to connect
reabsorption in organ culture and animal
the manometer and syringe containing the
models (Kallio et al, 1972; Azria, 1989).
oxygen. The clamp on the left was switched
Lack of estrogen is one of the leading causes
back to “open”. The different between the
of bone loss in aging women, including
level in the left and right tubes of the
secondary
hyperparathyroidism,
and
manometer was observed to estimate the
impairment
osteoblast
Thus,
volume of oxygen needed to be injected.
calcitonin treatment may be beneficial in
After which, the thyroid was palpated to
diseases directly associated with increased
manually check the size of the thyroid to
bone reabsorption.
determine if a goiter is present. The same
that
decreases
function.
procedure was done to the thyroidectomized
2 | MATERIALS AND METHODS
(Tx) and the hypophysectomized (Hypox).
For this PhysioEx activity, the group will be
2.2 | Determining the Effect of Thyroid
needing a desktop or a laptop with PhysioEx
Hormone on Metabolic Rate
9.1 installed in it to access Experiment 4,
Three rats were injected wit a syrine gilled
Activities 1 & 3.
with thyroxine for 1-2 weeks. The weight of
the rat, the amount of oxygen consumed by
3.1 | Determining the Basal Metabolic Rate
the rat within per minute & per hour, the
Three rats were subjected to weighing and
metabolic rate of the rat, and the result of
caging for this part of the activity. First, the
thyroid palpitation was also determined using
normal rat was put in an airtight, glass animal
the said procedure. The rat was placed back
chamber, and was weighed using an animal
to its cage, and cleared of all any thryoxine
weighing scale. Then, the clamp on the left
traces. The same procedure was repeated to
tube of the chamber was switched to “close”
determine the effect of TSH on the metabolic
to prevent any outside air from entering the
rate of the rats that were injected with TSH.
Endocrine Physiology: Metabolic Rate in Mice/Rats | 3
2.3 | Hormone Replacement Therapy
1536.59, and 1524.59 for the Normal, Tx,
Three rats were used for this activity – one
and Hypox. Goiter was not observed on the
control rat, one estrogen-treated rat, and a
Normal and Tx rats due to the palpitation of
calcitonin-treated
the thyroid.
rat.
All
rats
were
ovariectomized prior to the activity. A
There are three categories that can be
syringe was filled with 1 mL of saline
derived from the computed BMR and they
solution, and was injected into the control
are the hypothyroid (low thyroid levels; BMR
rat’s lower abdominal area. The same
less than 1600), euthyroid (good or normal
procedure was applied for the other two set-
levels,
ups using 1 mL of estrogen and 1 mL of
hyperthyroid (high thyroid levels, BMR
calcitonin for the the two remaining rats,
above 1800). Normal rats are classified under
respectively. This process continued for 7
euthyroid since nothing was done to the
more days with each rat receiving one
normal rat. And, both the Tx and Hypox rats
injection per day. Afterwards, the rats were
were hypothyroid since both of their BMR
immobilized with the use of anesthesia, and
are balow 1600. The lower BMR is due to the
were subjected to X-Ray scanning. Lastly,
surgical removal of the thyroid gland for the
the T-score was recorded.
Tx and the removal of the pituitary gland for
BMR
1640-1750),
and
lastly
the Hypox. Goiter was not observed since it
3 | RESULTS AND DISCUSSION
only occurs when the TSH levels are too high
causing it to enlarge.
3.1 | Metabolism and Thyroid Hormone
The basal metabolic rate of the Normal,
Hypox, and Tx rat as acquired by measuring
the weight of the rats and getting and its
respective oxygen consumption. The Normal
rat having the weight of 250 grams while the
Tx and Hypox had 246 had 244 respectively.
The measured oxygen consumption er minute
of the Normal, Tx, and Hypox are 7.1, 6.3,
and 6.2 respectively. The BMR was later
computed with the results being 1704.00,
Table 1. BMR and Palpitation of Rats
3.2 | Injection of Thyroxine
The second set up is done by injecting
Thyroxine in all the rats and after the initial
injection of thyroxine the BMR of the rats
were computed and its shows that all of the
Endocrine Physiology: Metabolic Rate in Mice/Rats | 4
rats classified as hyperthyroid since all of
their BMR are above 1800. The normal rat is
the one having the greatest BMR since unlike
the Tx and Hypox the rat still had its pituitary
and thyroid gland meaning the body of that
rat still produced thyroxine. There is also an
Table 3. BMR and Palpitation of Rats injected with
observed increase in oxygen consumption
TSH
since the increased level of thyroxine causes
the tempreture of the body to rise making the
3.4 | Injection of Prophylthioracil
rats consume more energy and intake more
In the fourth set-up prophylthioracil (PTU)
oxygen.
was injected to the three rats and the results
are that all the rats were classified as
hypothyroid since PTU is a drug that inhibits
the secretion of thyroxine in the body.
However, due to the PTU the TSH in the
thyroid accumulated causing it to enlarge and
Table 2. BMR and Palpitation of Rats injected with
therefore caused it to develop goiter on all of
Thyroxine
the rats except the Tx rat since it does not
3.3 | Injection of Thyroid Stimulating
have a thyroid.
Hormone
For the third set up TSH was now injected to
all of the rats. The normal and the hypox rats
were considered hyperthyroid since the
injected TSH caused their thyroid to secrete
Table 4. BMR and Palpitation of Rats injected with
excess amounts of thyroxine while the Tx rat
Propylthioracil (PTU)
remained hypothyroid since the rat had no
thyroid to be stimulated with.
Endocrine Physiology: Metabolic Rate in Mice/Rats | 5
4 | CONCLUSION
This exercise was able to justify the
Chiamolera, M.I. & Wondisford, F. (2013).
importance of the thyroid hormone when
Thyrotropin-Releasing Hormone and the
regulating
Thyroid Hormone Feedback Mechanism.
and
maintaining
the
basal
metabolic rate. Organs that participate in
Endocrinology.
3(150).
thyroxine-releasing pathways affect the
http://dx.doi.org/10.1210/en.2008-
thyroxine level, and in turn, also affect the
1795#sthash.VXccq0Kl.dpuf
metabolic rate. The injection of estrogen
made the rat normal from an osteoporotic
Doros, R., Delcea, A., Mardare, L., & Petcu,
state while the injection of calcitonin made
L. (2015). Basal Metabolic Rate in Metabolic
the rat osteopenic from, and osteoporotic
Disorders. THE PUBLISHING HOUSE OF
state. Thus, both estrogen and calcitonin
THE
improved the bone structure, and can be
Retrieved February 28, 2019.
therefore
used
in
ROMANIAN
ACADEMY,137-143.
hormone-replacement
therapy.
Kallio DM, Garant PR, Minkin C. (1994).
Ultrastructural effects of calcitonin on
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