Interactions of Prolactin and Adrenocorticotropin in the Regulation of Adrenocortical Secretions in Female Rats*

Abstract

Effects of PRL and ACTH alone and in combination upon adrenal function of hypophysectomized female rats were examined in vivo and in vitro. In vivo studies consisted of measuring hormone concentrations in peripheral plasma and in the venous effluent of the left adrenal gland. Secretion rates of corticosterone and its principal reduced metabolites [5α-dihydrocorticosterone (DHB) and 3β,5α-tetrahydrocorticosterone (THB)] were calculated. Adrenal 5α-reductase activity and production of corticosterone and total corticoids by adrenal homogenates and adrenal slices were studied in vitro. Removal of the pituitary elevated adrenal 5α-reductase activity. As a result, corticosterone was rapidly converted to DHB and THB. Administration of PRL to hypophysectomized rats resulted in decreased adrenal 5α-reductase activity and concomitantly increased the secretion of corticosterone in adrenal effluent by 79%. The peripheral plasma concentration of corticosterone was enhanced similarly. Secretion of corticosterone relati...