Anterior Pituitary and Lactation

Abstract

By injection of the anterior-pituitary-like hormone (A.P.L.) of pregnancy urine Evans and Simpson 1 were successful in producing marked development of the mammary glands in virgin rats, but were unable to produce milk secretion; Bradbury 2 obtained similar results in mice. We have confirmed these results by histological examination, which shows that no secretion takes place in the glands, although the alveoli are as numerous as in late pregnancy. We further observed that the development of the mammary gland in these animals runs parallel to the increase in the weight of their ovaries.

We found, however, that removal of the intensely luteinized ovaries of these rats will lead to abundant milk secretion in their mammary glands within 36 hours (13 experiments, all positive). We further observed that if the pituitary was removed simultaneously with the ovaries, milk secretion did not set in (4 experiments).

These experiments seem to indicate that removal of the luteinized ovaries will lead to milk secretion in the fully developed mammary gland of the A.P.L. treated rat, but only in the presence of the pituitary.