The endocrine system is the second greatest control system of the body and has many effects on the tissues and organs. The thyroid gland, which is a part of the endocrine system, releases a hormone that maintains metabolism. This hormone is thyroxine. Thyroxine production is controlled by thyroid stimulating hormone, which is released by the pituitary gland.
TSH stimulates the thyroid gland to produce thyroxine. In this experiment, the effects of TSH and thyoxine on metabolic rate are investigated. Estrogen is a hormone produced by the ovaries that helps the uterus to develop. The removal of the ovaries eliminates the source of estrogen and the uterus cannot develop properly. In one of the following experiments, the effect of hormone replacement therapy is investigated. Insulin regulates blood glucose levels and is produced by the pancreas.
When the pancreas does not produce insulin, the cells cannot absorb glucose from the blood. This results in diabetes mellitus type I. In one of the following experiments, the effects of insulin treatment are investigated for type I diabetes. HypothesisExperiment 1: Determining Baseline Metabolic RatesI hypothesize that the metabolic rate will be greater for the normal rate, then the thyroidectomized rat. The hypox rate will have the lowest metabolic rate.
Experiment 2: Determining the Effect of Thyroxine on Metabolic RateI hypothesize that metabolic rate will increase with the injection of thyroxine. Experiment 3: Determining the Effect of TSH on Metabolic RateI hypothesize that the injection of TSH will increase the metabolic rate of the all the rats except for the thyroidectomized rat. Experiment 5: Hormone Replacement TherapyI hypothesize that the rat receiving estrogen injections will have heavier more developed uterine tissue. Experiment 7: Comparing Glucose Levels Before and After Insulin InjectionI hypothesize that glucose levels of the diabetic rat will be closer to the glucose levels of the normal rat after the insulin injection.
Materials and MethodsThe materials used for this lab were the PhysioEx 6. 0, the Human Anatomy & Physiology Lab Manual and the computer. Experiment 1: Determining Baseline Metabolic RatesA normal rat was placed in the chamber and weighed. The clamp was then closed and the timer set to 1 minute.
After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat. Experiment 2: Determining the Effect of Thyroxine on Metabolic RateA normal rat was injected with thyroxine and placed in the chamber and weighed.
The clamp was then closed and the timer set to 1 minute. After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat.
Experiment 3: Determining the Effect of TSH on Metabolic RateA normal rat was injected with TSH and placed in the chamber and weighed. The clamp was then closed and the timer set to 1 minute. After 1 minute the manometer and syringe were connected and the clamp was opened. Air was injected into the tube until the fluid in each arm of the U-tube was level. The amount of O2 used in an hour was calculated and the metabolic rate for the normal rate was obtained. This process was repeated for the thyroidextomized rat and the hypopysectomized rat.
Experiment 5: Hormone Replacement TherapyA control rat was given 7 injections of saline over 7 days and an experimental rat was given 7 injections of estrogen over 7 days. The uteruses from each rat were removed and weighed. Experiment 7: Comparing Glucose Levels Before and After Insulin InjectionA control rat was given a saline injection and an experimental rat was given an alloxan injection. Both rats were given an insulin injection.
Blood was drawn from both rats and the glucose levels were compared. ResultsExperiment 1: Determining Baseline Metabolic RatesThe baseline metabolic rate for the normal rat was 1682. 7 ml O2/kg/hr, the rate for the thyroidectomized rat was 1473. 6 ml O2/kg/hr, and the rate for the hypox rat was 1473. 0 ml O2/kg/hr. Baseline Normal Rat Thyroidextomized Rat Hypophysectomized RatWeight 249.
6 244. 3 244. 4ml O2 in 1min. 7.
0 6. 0 6. 0ml O2 in 1 hour 420. 0 360. 0 360.
0Metabolic Rate 1682. 7 1473. 6 1473. 0Experiment 2: Determining the Effect of Thyroxine on Metabolic RateThe metabolic rate was calculated after the rats had been injected with thyroxine. The metabolic rate for the normal rat was 1802.
9 ml O2/kg/hr, the rate for the thyroidectomized rat was 1720. 6 ml O2/kg/hr, and the rate for the hypox rat was 1712. 1 ml O2/kg/hr. With Thyroxine Normal Rat Thyroidextomized Rat Hypophysectomized RatWeight 249.
6 244. 1 245. 3ml O2 in 1min. 7.
5 7. 0 7. 0Ml O2 in 1 hour 450. 0 420.
0 420. 0Metabolic Rate 1802. 9 1720. 6 1712. 2Experiment 3: Determining the Effect of TSH on Metabolic RateThe metabolic rate was calculated after the rats had been injected with TSH.
The metabolic rate for the normal rat was 1802. 2 ml O2/kg/hr, the rate for the hyroidectomized rat was 1522. 1 ml O2/kg/hr, and the rate for the hypox rat was 1708. 7 ml O2/kg/hr.
With TSH Normal Rat Thyroidextomized Rat Hypophysectomized RatWeight 249. 7 244. 4 245. 8ml O2 in 1min. 7.
5 6. 0 7. 0ml O2 in 1 hour 450. 0 360.
0 420. 0Metabolic Rate 1802. 2 1473. 0 1708. 7Experiment 5: Hormone Replacement TherapyThe uterus of the rat that received injections of estrogen was found to weigh more than that of the rat that received injections of saline. Rat Elapsed Days # Saline injections # Estrogen injections Weight of UterusControl 7 7 0 .
1073 gmsExperimental 7 0 7 . 6681 gmsExperiment 7: Comparing Glucose Levels Before and After Insulin InjectionTest Tube Opt Density Glucose Insulin Saline Alloxan1 normal . 62 87 No Yes No2 alloxan . 87 129 No No Yes3 nor/insulin . 62 87 Yes Yes No4 all/insulin . 68 96 Yes No YesDiscussion and ConclusionsThe results for the baseline metabolic rate were as expected.
The metabolic rates of the Tx and the Hypox rat were lower than the metabolic rate of the normal rat. The Tx rat could not produce thyroxine because it had no thyroid gland. The Hypox rat could not produce TSH which stimulates the thyroid to produce thyroxin. The results of the thyroxine metabolic rate were as expected. The injection of thyroxine increased the metabolic rate for all rats. This is understandable as thyroxine is the most important hormone in maintaining metabolism.
The injection provided the Tx rat with a source of thyroxine in place of the thyroid gland. The injection provided thryoxine for the Hypox rat in the absence of the pituitary gland to release TSH to stimulate the thyroid gland to produce thryoxine on its own. The results of the TSH metabolic rate were as expected. The metabolic rates for the normal and Hypox rats increased from the baseline rate. The injection of TSH would have had no effect on the Tx rat, as there was no thyroid gland to stimulate to release thyroxin.
The injection provided the Hypox rat with a source of TSH to stimulate production of thyroxin in the thyroid gland. Factors that may have changed the results of the experiment would be human error. If a step were missed, such as forgetting to clean the syringe after each use, it would affect the results. There may be a problem with the software and this would definitely affect the results.
This lab could have been completed in class with each lab, which would have been very interesting, although, I would not have enjoyed killing the rat at the end of the hormone replacement experiment. Another option would have been to have a more interactive computer simulationReferencesMarieb, Elain (2006). Human Anatomy & Physiology Laboratory Manual. 8th ed.
Pearson Education, Inc. Zao, Peter (2006). PhysioEx Version 6.0
