7. Endocrine System- Hormones

Lab Date: February 25, 2010

 

In this lab we conducted simulated experiments on rats testing differing effects of hormones using the PhysioEx web program.

 

The effect of thyroxine, THS, and propylthiouracil on the metabolism of a normal rat, a thyroidectomized rat, and a hypophysectomized rat.

In the first set of tests we tested the metabolic rates of each rat at baseline, each with thyroxine injected, each with TSH injected, and each with propylthiouracil injected and compared the results. 

In the normal rat injection with thyroxine made the metabolic rate go up, injection with TSH made the metabolic rate go up, and injection with propylthiouracil made the metabolic rate go down.

In the thyroidectomized rat injection with thyroxine made the metabolic rate go up, injection with TSH had minimal effect on metabolic rate (it went down slightly), and injection with propylthiouracil also had minimal effect on metabolic rate ( it also went down slightly).

 

IN the hypophysectomized rat injection with thyroxine made the metabolic rate go up, injection with THS made the metabolic rate go up, and injection with propylthiouracil made the metabolic rate go up. 

 

This experiment examined the interconnectedness and role that each hormone has on metabolism. Thyroxine is the major regulator of metabolism, but without a thyroid to produce it metabolism will slow.  Additionally, Thyroid Stimulating Hormone (TSH) needs to send a message from the pituitary gland to the thyroid to produce thyroxine, and therefore without a pituitary gland the metabolism will also be slow. In the hypophysecotomized rat the propylthiouracil did not work to inhibit thyroxine and the metabolism went up, indicating that a pituitary gland needs to be present for the propylthiouracil to work.

 

Hormone Replacement Therapy

In this experiment we removed the ovaries of two rats.  One rat was the control rat and received only saline, the other rat received hormone replacement therapy with daily injections of estrogen, the hormone the ovaries make.  At the end of the simulated seven day experiment the uteruses were removed and weighed.  The result was that the uterus of the control rat (with no hormone replacement) had a much smaller uterus (0.1047g) than the one that had had hormone replacement(0.665g).  This is because the size/weight of the uterus probably remained stable through hormone replacement(uterine cells reproduced with estrogen present), while the rat with no hormone replacement's uterus probably atrophied. 

 

Insulin and Diabetes

In this experiment we studied how insulin production and function are related to diabetes.  One rat was the control rat, and the other rat was treated with alloxan which selectively kills pancreatic β-cells that produce insulin.  We then tested the blood glucose levels with no insulin added to the blood and insulin added to the blood of each rat.  In the control rat, addition of insulin had no real effect on blood glucose levels because the insulin present was already working.  In the blood of the rat treated with alloxan the glucose level went down because the rat needed the extra insulin to process the glucose in the blood.


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