Abstract
Physiological saline (0.85%) or 2 mg doses of ACTH, cortisone or hydrocortisone were injected daily for 10 days into 42 intact, mature female rats. All 3 hormones elicited branching of ducts, lobule-alveolar development and secretory activity in mammary glands. This was most marked for cortisone and least for ACTH at the dose levels employed. Cortisone increased pituitary prolactin content by about 23%, hydrocortisone by about 41% and ACTH by about 71%. It is concluded that these hormones can initiate mammary development and secretion in the intact rat, but their normal role is not established.