Biological properties of 17-ethinyl-7α-methyl-19-nortestosterone (U-13,851)

Abstract

U-13,851 (17-ethinyl-7α-methyl-19-nortestosterone) exhibited both estrogenic and progestogenic properties in several biological test systems and was found to be 10 to 40 times as potent as norethindrone in comparative assays. U-13,851 prevented conception in rats at 100 μg/day orally and at one-half that dose systemically. This compound was tested in several biological assays to measure various hormonal effects. U-13,851 exhibited estrogenic activity in that it induced vaginal estrus at 20 μg/day rat. Its estrogenic activities were suggested also in the deciduomata assay and in the pregnancy maintenance test. U-13,851 did not exhibit any antiestrogenic potency against estradiol-induced uterine growth. It was active in the endometrial proliferation assay which is an indication of progestational activity. Tested for androgenic activity, it stimulated growth of seminal vesicles and the levator ani but was relatively inactive in stimulating prostate gland growth. Continuous medication suppressed the cyclic changes in vaginal smears of rats; recovery from long term medication was rapid and complete. Adrenal gland weight was unaltered by U-13,851; thymic weights were significantly depressed.