Relation Between Mammary-Gland Responses to Lactogenic Hormone Combinations and Tumor Susceptibility in Various Strains of Mice2

Abstract

The mammary glands of 12-week-old female mice of 10 strains and sublines of differing mammary-cancer susceptibility were studied in intact, hypophysectomized-ovariectomized and hypophysectomized-ovariectomized animals given lactogenic hormonal combinations that included somatotropin or mammotropin. Variations occurred in normal mammary-gland morphology among the different strains, but these could not be correlated with the mammary-cancer susceptibility of the strain. Regression of the mammary parenchyma occurred after hypophysectomy-ovariectomy in all strains examined. In all mice treated with estrogen plus progesterone plus mammotropin followed by mammotropin plus cortisol, lobuloalveolar development and lactogenesis occurred. The degree of response varied in different strains, but the variations could not be correlated with mammary-cancer susceptibility. In mice treated with estrogen plus progesterone plus somatotropin followed by somatotropin plus cortisol, lobuloalveolar development and lactogenesis occurred in genetically susceptible strains that show a high mammary-tumor incidence in both virgin and parous females. No such response was obtained in genetically susceptible strains with a high incidence only in parous females. The lobuloalveolar and lactational responses to somatotropin appear to be modified quantitatively by the presence or absence of the mammary-tumor agent.