THE EFFECT OF DIETHYLSTILBESTROL ON THE IMMATURE RAT OVARY1

Abstract

Hypophysectomized and intact immature female rats were injected with dicthylstilbestrol in daily doses of 1 mg. or 1 ¼g for periods of 2–20 days. The large doses increased ovarian weights to an average of 37 mg. on the 8th day in both the intact and hypophysectomized groups, after which a gradual decline occurred for the duration of the experiment. In hypophysectomized animals, ovarian weights were significantly greater than those of uninjected controls for the entire experimental interval. This was true in intact animals until 11 days, after which control ovaries were heavier owing to luteinization. The small dose of stilbestrol did not significantly increase ovarian weight in hypophysectomized rats, although some follicular growth was noted microscopically. In intact rats, the small dose increased ovarian weights at 8 days, apparently through intermediary release of pituitary gonadotrophin. This study confirms previous investigations in showing that large doses of stilbestrol cause growth and maintenance of medium-sized follicles in rat ovaries. The demonstration of similarities in weight increases and histological findings in intact and hypophysectomized rats provides further evidence for a direct action of stilbestrol on the ovary.