Experiment 4
The Set-up for Determining the Basal Metabolic Rate of a Normal Rat (Rattus norvegicus) M. S. Abad, A. P. D. G. Abeleda, C. G. S. M. Arce and K. B. Bautista Department of Biological Sciences, College of Science, University of Santo Tomas, España, Manila, Philippines Keywords:
Summary
Introduction
hypophysis, or the anterior pituitary gland. The production of TSH is controlled by the Thyrotropin-releasing hormone, which is released by the hypothalamus.
The endocrine system is one of the two organ systems (the other being the nervous system) that functions in control and communication of the body. Hormones, which are chemical messengers, are secreted from endocrine glands into the bloodstream then to the target cell. They play important roles in regulating a variety of physiological processes, thus maintaining homeostasis. They also control long-term responses throughout the body. Metabolism is defined as all of the biochemical reactions that occur in the body of living organisms; and metabolic rate is measured as heat production per unit time. The metabolic rate in mammals is set by the thyroid hormones, which are secreted from the thyroid gland. 3, 5, 3', 5' tetraiodothyronine (T4 or Thyroxine) and 3,5,3' triiodothyronine (T3) are collectively termed as the thyroid hormones. They are hydrophobic, unlike most biogenic amines. They are released via diffusion from the lysosome upon degradation of the thyroglobulin protein. Thyroid-stimulating hormone (TSH) regulates the secretion of the thyroid hormones. This is produced by the
Determining the Thyroid-stimulating hormone levels in the body is generally used to measure thyroid function. Normal levels indicate euthyroidism, while abnormal levels indicate either hypothyroidism or hyperthyroidism. This experiment aims to observe and understand the set-up used for basal metabolic rate measurement as well as determine the basal metabolic rate of a normal rat. Materials and Methods
A
B
Fig 1.A Hypothetical set-up for Basal Metabolic Rate (BMR) measurement; 1.B Actual set-up used for BMR measurement The set-up used to determine the basal metabolic rate measurement consisted of a glass animal chamber, rubber tubing, a clamp, a t-connector, soda lime, a manometer, syringe, an animal scale, and a normal rat. In the set-up, the airtight, glass animal chamber was used in order to provide an isolated and closed system for measuring the amount of oxygen consumed by the rat. This ensures that no outside air will enter during a given amount of time. This chamber is connected to rubber tubing, where a clamp on the left side allows outside air passage into the chamber while equalizing the manometer levels, and a t-connector on the right connects the chamber to the manometer and the syringe.
Soda lime was used to absorb the carbon dioxide (CO2) exhaled by the rat to assure the measurement of pure oxygen. A manometer was used to measure the pressure, wherein consumption of oxygen by the rat will lead to fluid rising to the left side of the tube. The syringe was used to introduce air into the tube, and measure the amount of air for the manometer levels to equalize. An animal scale was used in determining the weight of the rat, and lastly, a normal laboratory rat was used to conduct the experiment. The weight of the rat was first measured using a scale. Then, it was placed in the glass animal chamber. The clamp on the left tube was closed to ensure a closed system. A timer was then set for one minute to measure the amount of oxygen consumed by the rat in the chamber. The t-connector was then used to connect the manometer and the syringe. Afterwards, the clamp was opened to allow outside air to enter the chamber. Air was then injected to equalize the level in the left and right arms of the manometer. Once the levels were equalized, the amount of oxygen injected (mL O2 consumed/1 minute) was recorded. The oxygen consumption per hour of the rat was computed using the following equation: (mL O2 consumed/1 min) x (60 minutes/hr) =mL O2/hr Lastly, the metabolic rate per kilogram of body weight was computed using the following equation: Metabolic rate= (mL O2/hr)/(weight in kg) =mL O2/kg/hr
Results and Discussion weight of rat (kg) mL O2/10 mins mL O2/ min mL O2/ hr BMR
0.19 1.7 0.17 10.2 53.68
preparation of the set-up or in conducting the experiment are probable reasons why the results obtained were questionable. Conclusion References
Basal metabolic rate is an indicator of thyroid function. Hypothyroidism or low thyroid levels, is characterized by a BMR that is less than 1600. Euthyroidism, or normal thyroidism is characterized by a BMR measure that ranges from 1650-1750. Lastly, Hyperthyroidism, or high thyroid levels, is characterized by a BMR that is greater than 1800.
Becker, K. L. (2001). Principles and practice of endocrinology and metabolism. Philadelphia: Lippincott Williams and Wilkins.
Based on the results obtained from the actual experiment, the rat is characterized to have hypothyroidism. However, the BMR calculated, which is 53.68, is abnormal and extremely low compared to the values of the ranges indicated. Therefore, the experiment is deemed to be inconclusive. Errors in
Moyes, C. D., & Schulte, P. M. (2008). Principles of animal physiology. San Francisco, CA: Pearson/Benjamin Cummings.
Endocrine System Physiology. (n.d.). Retrieved February 25, 2016, from http://helios.hampshire.edu/~cjgNS/sputtbug /416K/Energy Reg/PhysioEx.pdf
Rushton, L. (2004). The endocrine system. Philadelphia: Chelsea House.
