INDUCTION OF MAMMARY SECRETION IN PREGNANT RATS AND RABBITS BY HYDROCORTISONE ACETATE1

Abstract

A dose of 2 mg. of hydrocortisone acetate (HCA) per day, injected during the 5–9th or 9–13th days of gestation in rats initiated mammary secretion on the 10th or 14th days, respectively. This treatment had no effect on duration of pregnancy or number of viable young at birth. The same dose of HCA also initiated mammary secretion in rats when administered during the 9–13th days of pseudopregnancy. All other hormones including prolactin, oxytocin, ACTH, and combinations of prolactin and ACTH or prolactin and oxytocin were ineffective at the dose levels used. A dose of 15 mg. HCA per day initiated copious milk secretion in rabbits on the 20th or 21st day of pregnancy when administered during the 16–19th days of pregnancy. A dose of 1 i.u. oxytocin given 3 times daily was ineffective in initiating lactation in the rabbits. It is suggested that the levels of biologically active adrenal glucocorticoids may not be sufficiently high during pregnancy and therefore may be partially responsible for the absence of mammary secretion during this state.