Somatotropin as the non-ACTH factor of anterior pituitary origin for the maintenance of enhanced aldosterone secretory responsiveness of dietary sodium restriction in chronically hypophysectomized rats

Abstract

Somatotropin treatment in chronically hypophysectomized, sodium-deprived rats effectively restored to treated animals the distinct and enhanced aldosterone secretory responsiveness of the adrenal which characterizes the adrenals of intact rats subjected to dietary sodium restriction, but absent in chronic and nontreated, adenohypophysectomized or totally hypophysectomized rats subjected to similar conditions of dietary sodium restriction. Treatment with β 1−24ACTH(Zn) alone was ineffective, albeit adrenal weight and glucocorticoid secretory responsiveness were effectively maintained. The observed efficacious effect of somatotropin is similar and indistinguishable from the previously demonstrated effect produced by treatment of anterior pituitary powder in chronically hypophysectomized, sodium-deprived rats. The earlier findings that somatotropin is without any direct or specific stimulatory effect on aldosterone secretion and that treatment of intact, sodium-repleted rats with anterior pituitary powder is devoid of any adrenoglomerulotropic influence on the observed refractoriness of the aldosterone secretory response to stimulation justify the inference that somatotropin is the relevant non-ACTH anterior pituitary factor imperative for the presumed normal maintenance of agencies which mediate the characteristic adrenocortical changes in aldosterone secretory capacity in intact, sodium-deprived rats.