Abstract
Summary
Six groups of immature male rabbits were injected 5 days weekly for 5 weeks with 30, 60, 120, 240, 480, and 960 LU. of estrone respectively. The best mammary duct growth occurred in the animals receiving 120 LU. The 30 and 60 LU. animals showed slightly less extensive duct systems, and the higher levels caused cystic changes in the main ducts.
The same 6 levels of estrone were injected into 6 other groups of male rabbits along with 1 I.U. of progesterone dairy for a similar period. In every case, lobular growth of the mammary glands occurred and no tendency toward cyst formation was noticed even in the animals receiving the highest level of estrone. The mammary glands of the animals receiving the 2 lowest levels of estrone, plus progesterone had not developed as extensively as the others, but showed good lobule formation on a relatively shorter duct system. The best prolactational proliferation was observed in the groups receiving 1 I.U. of progesterone plus 240 and 960 I.U. of estrone respectively. Only the presence of incomplete lobules at the periphery of these glands made possible their differentiation from glands taken from rabbits in their second to third week of pregnancy—a period when prolactational proliferation is usually maximal.
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