EFFECT OF HYPOTHALAMIC LESIONS AND HYPOPHYSECTOMY ON CORTICOID PRODUCTION IN VITRO AND ON ADRENAL WEIGHT IN RATS

Abstract

ABSTRACT Intact, sham-operated, hypophysectomized rats and rats bearing extensive lesions in the median eminence were stressed by ether anaesthesia. The pituitary-adrenal response to the stress was determined on the in vitro steroidogenesis by adrenal gland slices of the left gland and on adrenal weight changes in the left and right gland. The absence of compensatory adrenal hypertrophy which normally occurs following the removal of the left gland, was used as an index of the inhibition of the secretion of ACTH (corticotrophin) from the adenohypophysis in the lesioned rats. Following ether stress, corticoid production in vitro of the left adrenal gland rose considerably in intact rats. Adrenal response to stress of sham-operated animals was almost similar to that of intact rats at 4, 66 and 162 hours but significantly depressed at 18 hours following operation. Hypophysectomized and lesioned rats, however, failed to exhibit an increased steroidogenesis in vitro following ether stress at the four time intervals studied. Pitressin markedly stimulated corticoidogenesis of adrenals of lesioned rats at 18. 66 and 162 hours following the production of lesions. The weight of the left adrenal gland of lesioned and hypophysectomized rats decreased gradually during the period studied; that of the latter group decreased at a faster rate. Adrenal hypertrophy, usually observed some time after placement of a lesion, did not occur in the lesioned rats of the present experiments. Weight increase of the right adrenal removed one week following extirpation of the left gland, was similar in intact and sham-operated rats, whereas this compensatory adrenal hypertrophy was absent in hypophys-ectomized as well as in lesioned animals.