Pharmacology Experiment - effect of thyroxine, TSH and Propyltiouracil on metabolism

Object – To study the effect of thyroxine, TSH and propyltiouracil on metabolism of the normal rat, thyroidectomyzed rat and hypophysectomyzed rat.

Reference – TripathiK.D: essentials of medical pharmacology Jaypee brothers medical publishers LTD, 2015.

Requirement- PC & Expharm software

Pharmacology Experiment - effect of thyroxine, TSH and Propyltiouracil on metabolism

Theory

Metabolism consists of the exchanges of matter and energy between the organism and the environment.

Its value depends on the following:

• Species (the larger the animal, the lower the value of metabolism)
• Sex (the metabolism of a male is more intense than of a female)
• Age (Older animal - the lower the value of metabolism)

The main hormones which are responsible for the regulation of metabolism are the thyroid hormones (thyroxine and triiodothyronine). They are synthesized by the follicular cells of the thyroid gland and their secretion is enhanced by TSH (thyroid-stimulating hormone) which is synthesized by the anterior lobe of pituitary gland.

Propyltiouracil is a substance which inhibit the synthesis of thyroid hormones.      

The intensity of exchange between organism and environment may be estimated by measuring the heat which comes out of the organism into the environment (calorimetry).

Direct calorimetry consists of measuring the heat which comes out of the organism into the environment per time unit. For this purpose a complex experimental device is necessary.

Indirect calorimetry offers the possibility to evaluate metabolism by means of simpler methods, which do not use complex experimental device. Such methods are : the methods of nutritive balance and the methods of respiratory exchange.

The method of respiratory exchanges relies on the principle the intensity of metabolism is proportional with the amount oxygen which is consumed by the organism in a time unit.

Metabolic rate = ml of consumed oxygen/kg/hour

The experimental device is made up of :

• Respiratory room with a closed circuit
• A simple manometer
• Sodium limestone (a substance which absorb carbon dioxide room the respiratory room).
• A device for introducing air in the respiratory room.

Rat

Procedure

• Introduction the normal rat in the respiratory room.
• Click the START button.
• Wait for 60 seconds and notice how the level of the liquid decrease in the left side of the manometer, as the oxygen from the respiratory room is consumed (in the same time, the carbon dioxide which is produced by the rat is absorbed by the sodium limestone).
• After 60 seconds, click the button in order to introduce air in the respiratory room, until the level of the liquid is the same in the two sides of the manometer.
• Determine the metabolic rate by the following formula :-

Metabolic rate = mo of oxygen * 60 * 1000 / rat of body weight

• Repeat actions from points 1,2,3,4 and 5 after administration of the rat – thyroxine, TSH and propyltiuracil.

Result -