Qualitative reaction to thyroxine.

The thyroid gland produces two hormones containing iodine, which can be regarded as derivatives of L-thyronine: triiodothyronine and tetraiodothyronine (thyroxine). They are formed by iodination of tyrosine, which is part of the thyroglobulin protein. In hypothyroidism edema, water retention in the tissues, reduced metabolism, fatigue, obesity are observed, In the lack of exogenous iodine endemic goiter develop. It is reactive overgrowth of the thyroid tissue. Thyroid gland hormones and drugs derived from it are used for therapeutic purposes.

Detection of thyroxine is carried out, splitting off hydrogen iodide from it by acidic hydrolysis. In the test tube add half tablets of thyroxine and 0,5 ml of concentrated nitric acid, gently heat for 1-2 minutes. Then add in the test tube 1 ml of 1% potassium iodate solutionf, stir and cool. Potassium iodate oxidizes the released during hydrolysis hydrogen iodide into free iodine:

In the test tube add 1-2 ml of chloroform and shake it well. After standing chloroform layer (bottom) is stained by iodine in purple.

Qualitative reactions to the 11-dehydro-17-oxykortikosteron (cortisone).

Corticosteroids have cyclopentaneperhydrophenanthrene ring in the basis of their structure. They are synthesized in the adrenal cortex from cholesterol. Corticosterone, cortisol, cortisone, aldosterone increase protein degradation and stimulate gluconeogenesis. Excessive intake of these hormones causes hyperglycemia and glycosuria. Deoxycorticosterone and aldosterone effect on mineral metabolism. Insufficiency of adrenocortical function leads to loss of sodium, bicarbonate and chloride in the urine along with a retension of potassium in the body.

The reaction with phenylhydrazine sulfate.

To 1 ml of 1% cortisone acetate solution add 5 ml of phenylhydrazine sulphate solution and heat on a water bath. After few minutes a yellow color appears. Coloration is due to the formation of phenylhydrazone and then ozazone by the carbonyl groups of cortisone.

4.2. The reaction with Fehling's reagent.

To 1 ml of 1% solution of cortisone acetate add 1 ml of Fehling’s reagent and heat it in a water bath. There is reddish-orange precipitate of copper oxide (I).

Test Questions

1. Give the definition of hormones.

2. How to classify the hormones?

3. Which classes are hormones that are identified in the laboratory work?

4. Briefly describe the molecular mechanisms of hormonal signal transduction.

Laboratory work 6.

Date: 2016-04-22; view: 781