Direct Mammotrophic Effect of a Pituitary Homograft in Rats

Abstract

Grafting a single pituitary gland subcutaneously in the hypophysectomized or hypophysectomized and ovariectomized rat induces profound alveolar lobular growth of the atrophic mammary glands. When an ovary is implanted simultaneously with the pituitary graft, the corpora lutea of the ovarian graft are maintained. The mammotrophic effect of the graft, however, is observed only in the mammary gland on the side where the pituitary graft is implanted; the contralateral gland remains atrophic. It is concluded that the pituitary graft exerts a direct mammotrophic effect on the mammary gland, and that this effect is independent of the presence or absence of ovaries and pituitaries in situ. The extent to which the mammary gland develops appears to depend only upon the amount of prolactin secreted by the pituitary graft, and steroid hormones are probably not needed.