STUDIES OF THE BIOLOGICAL ACTIVITY OF CERTAIN 19-NOR STEROIDS IN FEMALE ANIMALS1

IN PREVIOUS publications a number of compounds have been demonstratedas inhibitors of ovulation in rabbits and rats (1, 2, 3). As ourstandard of reference we have used progesterone, which appears to beeffective also in women (4,5). Of especial interest are four compounds:17a-ethinyl-19-nortestosterone (I), 17a-ethinyl-5(10)estraen-17/3-ol-3-one(II), 17a-ethyl-19-nortestosterone (III), and 17a-methyl-19-nortestosterone (IV). These compounds have been suudied for: (a) progestational activity inrabbits, (b) deciduomagenic capacity in rats, (c) estrogenic activity, (d)ovulation-inhibiting activity in rabbits and rats, and (e) effects on developmentof the ovulated ovum. Progestational activity in rabbits The progestational activity of the various compounds was tested by theClauberg (6) method. Immature, grey Chinchilla, female rabbits weighingapproximately 1 kg. were used in this study.