The endocrine system and metabolism

Introduction

The endocrine system plays an essential role in regulating the functions of every cell, tissue, and organ in the body of a living organism (Beckett, 2005). Regardless of the changes in and outside the body, it acts by maintaining a favorable internal body environment. The cells of the endocrine system can sense and respond to changes through the excretion of specific substances called hormones. Hormones are substances that are carried by the blood and are generally attached to specific plasma proteins (Norman, 1997). Hormones circulate the body. Metabolism refers to all chemical reactions that are involved in the maintenance of the living state of a cell and organism. Metabolism is classified into two categories. Catabolism involves the breaking down of molecules to obtain energy, whereas anabolisms involve the synthesis of the compounds that are required by the cell (Baxter, 1985).

The hypothalamus plays a significant role in the sensing and integration of signals from the periphery and creates an appropriate effect on physiological changes to maintain homeostasis. The hypothalamus, which is located in the brain, is the main endocrine gland, and it secretes several hormones that affect the pituitary gland. If the hypothalamus realizes that there is an insufficiency of thyroxin circulation, which maintains the body’s metabolism, it immediately secretes the thyrotropin-releasing hormone, which stimulates the production of thyroid-stimulating hormone by the pituitary gland. The pituitary gland, therefore, stimulates the production of thyroxin by the thyroid (Holmes, 1974).

Methods

In this experiment, the baseline metabolic rate of each rat is determined by performing the following. The normal rate is dragged into the chamber and place on top of the scale. The mouse button is released when the rat is in the weighing scale. The clamp on the left tube should be open to allow the air to enter into the chamber. The indicator next to the t-connector should be reading “connected.” The weigh button is clicked to weigh the rat. The weight obtained recorded as the baseline metabolic rate of the rat.

The plus button on the timer clicked so that it shows 1.00. The clamp closed to prevent any air from the outside from entering into the chamber. The air that the rat should be breathing is the air inside the closed chamber. The timer started, and an observation made on what happens on the water level in the u-shaped tube. The timer stops automatically at the end of the 1 minute. The t-connector knob clicked to indicate a manometer and syringe connected. The clamp clicked to open, and the rat breath outside air. The difference between the level of water in the left and the right arms of u shaped tube. The oxygen consumption per hour by the rat is determined.

In the experiment, three types of rats used, i.e., normal rat, thyroidectomized rat, and hypophysectomised rat. The thyroidectomized rat is a rat without a thyroid gland, whereas the hypophysectomised rat is a rat without the pituitary gland. The three rats used were similar in the sense that all are used to determine the baseline metabolic rates, the effects of thyroxin, thyroid-stimulating hormone, and propylthiouracil.

In the determination of the effects of thyroxin on the metabolic rate, the following were done: a rat was chosen for the test. The reset button was clicked, and the syringe labeled thyroxin picked and dragged to the rat. This results in the injection of thyroxin into the rat. The rat is pulled back into the chamber. The same activity as determining the baseline is performed and recorded as thyroxin. The rat dragged out of the chamber to its cage. The effects of TSH on the metabolic rate is determined by clicking and dragging the syringe labeled as TSH. This results in the injection if TSH to the rat. The rat dragged into the chamber and the same activity as in determining the baseline of metabolic rate performed. The data is recorded as TSH. The effects of propylthiouracil on metabolic rate are determined by dragging the syringe labeled propylthiouracil to the rat, hence the injection of the rat. The rat is pulled back into the chamber, and the same activity performed in determining the effects of baseline on metabolic rate is done—the data recorded as propylthiouracil.

Results

Table 1. A summary of Activity 1-4 metabolic rates data for each rat

Figure 1. A bar chart showing metabolic rates for each rat

Summary

The weight of all the three rats ranges from 245-250 grams. The amount of oxygen used per minute by all the three types of rats ranges from 6-7ml. The results, therefore, mean that the amount of energy used for metabolism for the rats is almost equal despite the difference. The bar chart is shown above (figure 1.) shows that the rate of metabolism on the baseline was very low as compared to when it was injected thyroxin. The rate of metabolism on the normal rat increased rapidly with the injection of the thyroid-stimulating hormone. On the injection of propylthiouracil, the rate of metabolism on the baseline decreases.

The rate of metabolism on the thyroidectomized rat is at a high level from the baseline. It increases with the injection of thyroxin and decreases with the injection of thyroid-stimulating hormone. The rate of metabolism with the injection of propylthiouracil is almost the same as with the injection of thyroid-stimulating hormone. It is seen that the thyroid-stimulating hormone decreases the rate of metabolism on both the thyroidectomized rat and the hypophysectomised rat. Thyroid-stimulating hormone stimulates the thyroid glands to produce thyroxin hence increasing the metabolic rate.

The rate of metabolism on the hypophysectomised rate is high at the baseline. It increases slightly with the injection of thyroxin. With the injection of thyroid-stimulating hormone, the rate of metabolism on the hypophysectomised rat also increases slightly. The rate of metabolism on the hypophysectomised rat decreases with the injection of propylthiouracil. Generally, the rate of metabolism in all three rats increases with the injection of thyroid-stimulating hormone.

References

Baxter, L. R. (1985). Cerebral metabolic rates for glucose in mood disorders: studies with positron emission tomography and fluorodeoxyglucose F 18. Archives of general psychiatry, 441-447.

Beckett, G. J. (2005). Selenium and endocrine systems. Journal of endocrinology, 455-456.

Holmes, R. L. (1974). The pituitary gland (Vol. 4). California: Univ of California Press.

Norman, A. W. (1997). Hormones. Chicago: Academic Press.