INTERACTIONS OF OESTROGENS AND ANDROGENS ON THE MAMMARY GLAND AND GROWTH OF OTHER TISSUES IN HYPOPHYSECTOMIZED RATS TREATED WITH INSULIN, CORTISONE AND THYROXINE
In a previous study it was found that oestrogens are necessary for androgens to elicit a development of alveolar lobules in the mammary glands of rats. Since androgens and oestrogens exert synergistic as well as antagonistic actions on mammary glands of e. g. rabbits, the significance of oestrogens in the response of the mammary gland to androgens was further investigated in the rat. The experiments were designed according to the same principles as previously, that is, the response of the gland itself to oestrogens was modified. This was achieved by treatment of hypophysectomized rats with a) thyroxine (negligible response) and b) thyroxine, cortisone and insulin (marked response). The effect of endogenous androgens was studied in males injected with PMS with or without oestrogens. Gonadecto-mized rats were injected with testosterone and oestrogens. 1) No oestrogens given The mammary glands of hypophysectomized males injected with PMS showed an abnormal response, irrespective of simultaneous treatment with thyroxine, cortisone and insulin in various combinations. The result confirms previous work with testosterone. 2) Negligible response of the mammary glands to oestrogens: In hypophysectomized rats treated with thyroxine, oestrogens and PMS or testosterone, the response of the glands was uniform and abnormal. The absence of end buds indicated that the response to oestrogens, if present at all, was suppressed by the androgens. 3) Marked response of the mammary glands to oestrogens: In hypophysectomized rats treated with thyroxine, cortisone and insulin another response of the glands to androgens and oestrogens was found. Besides abnormal structures, alveolar lobules were present. The changes produced with different doses of testosterone and oestrone indicated a complicated interplay of the two hormones. 4) Confirming previous observations, records of the length and weight of the body and of the weight of the liver and heart revealed marked growth in the hypophysectomized rats treated with thyroxine, cortisone and insulin.