Effect of Stilbestrol on the Mammary Gland of the Mouse, Rat, Rabbit, and Goat

If knowledge of the hormonal causes of the growth and lactation of the mammary gland is to be put to practical use it will be necessary to find cheap sources of the hormones and devise simple and effective methods of administration.This report is concerned with a first step in that direction.Work in this laboratory has shown that the estrogenic hormones stimulate growth of the mammary duct system by increasing the rate of secretion of mammogen by the pituitary (1).The recent synthesis of a compound called stilbestroI, which has very great estrogen-like physiological activity and still is relatively inexpensive in comparison to the natural estrogens, has stimulated considerable research.Stilbestrol has the further advantages that it is quite effective orally and when formed into pellets is slowly absorbed for months when implanted under the skin (2, 3, 4, 5).This chemical, which simulates the estrogens in its physiological properties, is produced at 1/50 the cost for equal activity.It is sufficiently low in cost at active dosages to consider its practical application in livestock therapy.With this in mind the authors are conducting experiments on the influence of stilbestrol on the mammary gland and milk secretion in laboratory and farm animals.Many stilbestrol experiments of clinical nature or having no application to'mammary development cannot be reviewed here (for these see ref. 6).Assays of the effect of stilbestrol on the genital organs show that one-half gamma produced estrus in 70 per cent of 175 gram spayed rats (7).Stilbestrol was found to be equal to, or five times as active as, estrone in producing vaginal eornification in rats and mice (4, 7, 8).Orally administered stilbestrol was twenty times as active in mice as estrone and 16 times as aetive as estradiol (7).Van tteuverswyn st al. (9) found that groups of five male mice given 0.05, 0.2, and 2.0 rag: of stilbestrol, respeetively, gave plus two, plus three and plus one rating of mammary duet responses after eight injections in 16 days.Stilbestrol was found to be about one-fifth as active as estrone in causing proliferation of themammary gland of spayed rats (10), and of guinea pigs (11).Received for publication May 12, 1941.