STIMULATION BY HORMONES OF RNA AND PROTEIN FORMATION IN ORGAN CULTURES OF THE MAMMARY GLANDS OF PREGNANT MICE

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Abstract
SUMMARY: Explants of the mammary glands of 11–13 day pregnant C3H mice have been cultured in a synthetic medium with hormone additions. In cultures with insulin and corticosterone the lumina of mammary alveoli became enlarged by 48 hr. but contained little or no visible secretion; alveolar cells were not vacuolated. The rate of incorporation of [14C]adenine into RNA, and the RNA content of these explants, had fallen by 48 hr. In cultures with insulin, corticosterone and prolactin, secretion was already present in the enlarged alveolar lumina by 24 hr. and had increased in amount by 48 hr. Many alveolar cells contained secretory vacuoles. The rate of incorporation of [14C]adenine into RNA had nearly doubled by 24 hr., and the RNA content of the explants had also increased. These increases were still evident at 48 hr. The rate of incorporation of [14C]adenine into RNA was also measured at 3-hr. intervals up to 12 hr. With insulin alone, the rate remained roughly constant over the 12 hr. With insulin, corticosterone and prolactin it began to rise after 6 hr. and was finally about twice the initial value. The rate also rose to a lesser extent after 6 hr. with insulin and corticosterone. After 12 hr. with insulin, corticosterone and prolactin the rate of incorporation of [14C]lysine into proteins was also higher than with insulin alone.