Lack of influence of hypophysectomy on estrogen-induced DNA synthesis in Leydig cells of BALB/c mice.

In mice of strains susceptible to Leydig cell tumor induction, treatment with estrogens induced a "spurt" of DNA synthesis within the first few days. This synthetic activity generally subsided, until areas of Leydig cell hyperplasia developed several months later. Autoradiographic and quantitative biochemical studies indicated that in BALB/c mice this initial DNA synthetic activity occurred in the absence of the hypophysis and apparently was the result of effects of estrogen directly on Leydig cells. Although hypophysectomy inhibited sperm maturation, [3H]thymidine incorporation into spermatogonia was reduced only slightly 2 weeks after surgery, as was the induced DNA spurt in the interstitial tissues.