STIMULATION OF MAMMARY GLANDS IN HYPOPHYSECTOMIZED RATS BY ESTROGEN AND TESTOSTERONE1

Abstract

Estradiol dipropionate stimulated end bud growth in immature hypophysectomized and 2 rats if (a) the normal healthy rats weighed less than 70 gs. at the time of operation, (b) injections were started immediately and continued for 10-12 days. No stimulation of the end buds was obtained if (a) the rats were significantly heavier than 70 gs. at the time of operation regardless of when hormone treatment was begun (b) at least 7 days elapsed before treatment was begun regardless of the age and wt. of the rat. It is suggested that the mammary gland cells retain for a certain period of postnatal life potentiali-ties for growth, at which time they can be stimulated by estrogen, but after this critical period, these potentialities are lost and the cells are unaffected by estrogen. Testosterone propionate induced a thickening of the ducts of the mammary glands of hypophysectomized rats regardless of age and weight and the period at which treatment was begun. This thickening was caused by dilation of the lumina of the ducts by some hyperplasia and hypertrophy of the epithelial cells. Secretory material was seen in the stimulated ducts arising from the cytoplasm of the epithelium. These results suggest that the pituitary mammogen acts synergistically with testosterone as an augmenting substance to give the more extensive hormonal effects of testosterone observed in normal rats.