Atrophy of the Thymus in Normal and Hypophysectomized Rats Following Administration of Cortin

Abstract

Moon 1 noted atrophy of the thymus in rats following administration of the adrenotropic principle of the anterior lobe of the pituitary glands. His observations have been confirmed by Lyons and Simpson of the same laboratory. 2

This investigation deals with the effect on the thymus of administering massive amounts of cortin to normal rats and to rats which had been hypophysectomized. Forty male rats, each having an initial body weight of 180 g, were used. Ten normal animals were untreated and 10 normal animals each received 10 cc of cortin daily in their drinking water (each cubic centimeter of cortin represented 75 g of adrenal glands). Twenty hypophysectomized rats each received an amount of adrenotropic hormone daily which previous assay had proved adequate to maintain the adrenal cortex in hypophysectomized rats. This adrenotropic hormone was prepared and furnished through the courtesy of Dr. H. D. Moon. Ten of the hypophysectomized animals were given 10 cc of cortin daily in their drinking water; the remaining 10 did not receive cortin. In this experiment the intake of food of the 2 groups of hypophysectomized rats was regulated in order to equate the loss of weight. It was necessary to restrict the intake of food in the case of the rats which did not receive cortin to a definitely smaller amount than was consumed by those which did receive cortin. At the end of 7 days all of the animals were killed for necropsy by exsanguination.

The administration of large amounts of cortin causes marked involution of the thymus in the intact rat. The loss of weight which occurred in these animals cannot he satisfactorily accounted for by the small reduction in the intake of food.