Diurnal Variation of Adrenocortical Function in Hypophysectomized Rats with Multiple Heterotopic Pituitary Homografts

Abstract

WE have shown that hypophysectomized male rats bearing ten heterotopic, homografted pituitaries under the renal capsules have nearly normal adrenal weight and considerable, though subnormal, adrenal corticosterone production¹. Because adrenal weight and production of corticosterone was markedly reduced in hypophysectomized rats without pituitary homografts, we concluded that the heterotopic pituitary has adrenal-maintaining activity presumably by means of the secretion of ACTH. Furthermore, because many investigators have shown that a single heterotopic pituitary exhibits only very slight adrenal-maintaining activity^2–4, we concluded that multiple heterotopic pituitaries maintain adrenal weight by virtue of their collective secretion of individually small amounts of ACTH. The present communication deals with studies of diurnal variation in the function of the cortex of the adrenal glands in rats with pituitary homografts and provides evidence that direct connexion between the brain and pituitary is not essential for the rhythmic activity of the pituitary-adrenocortical axis.