EFFECT OF INSULIN ON BODY GROWTH AND MAMMARY GLAND DEVELOPMENT IN FORCE-FED HYPOPHYSECTOMIZED RATS INJECTED WITH OVARIAN HORMONES

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Abstract
Body growth and mammary gland development was studied in groups of castrated female rats which included: (1) hypophy-sectomized rats given a semisynthetic diet ad libitum and injected with ovarian hormones and zinc protamine insulin. These rats tolerated daily injections of up to 2-6 I.U. of insulin. During treatment, their food intake increased markedly and they gained slightly in weight. Mammary gland development was very limited. (2) Force-fed hypophy-sectomized rats injected with ovarian hormones gained markedly in weight but did not increase in body length. They did not show mammary gland development in spite of increases in the body weight of as high as 152%. (3) Force-fed hypophysectomized rats injected with ovarian hormones and zinc protamine. Administration of insulin in gradually increasing doses (up to 40 I.U. of insulin daily) had no clear effect on body weight or body length in the force-fed rats. However, the insulin-treated rats showed a marked growth of the mammary glands.