Experimental Growth of Mammary Gland in Male and Female Mice. ∗

Summary

1. Maximum growth of the lobule-alveolar system of mammary gland, as measured by total DNA, in ovariectomized female and estrogen-primed male mice(to develop duct system) was observed when 1 μg estradiol benzoate and 3 mg progesterone were administered daily for 19 days.(2) Maximum total DNA experimentally stimulated in female mice, on an equal weight basis, was only 57.6% of the DNA observed in normal mice pregnant 18 days.(3) Corresponding value for males was 48.3%.(4) These data suggest that a hormone of placental origin may be involved in mammary gland growth other than ovarian hormones.(5) On an equal body weight and gland basis, the mammary glands of mice at end of pregnancy contain approximately 150% as much DNA as do rats.