Ability of deglycosylated human chorionic gonadotropin (dghCG) to block luteal function and establishment of pregnancy in bonnet monkeys (Macaca radiata).

The ability of deglycosylated hCG (dghCG) prepared by deglycosylation of a clinical hCG (3000 IU/mg) preparation, to block luteal function during regular cycles as well as luteal rescue in simulated and mated cycles of female bonnet monkeys (M. radiata) has been evaluated. The cycle length (C:28 vs E:24 days) and the total progesterone produced during the luteal phase was significantly reduced (by 45%, P < .05) by injecting 450 micrograms of dghCG/day (in split doses) on days 18, 19, and 20 of cycle. At the doses tested the dghCG used did not exhibit any agonistic activity in the female monkey. In a second experiment injection of 200 micrograms of dghCG/day on days 18-20 of cycle blocked the normal response of the luteal tissue to exogenous hCG (10 micrograms of a 12,000 IU/mg preparation) injected on day 23 of cycle. In a third experiment no pregnancies occurred when a group of 5 animals were injected dghCG (450 micrograms dghCG/day) on days 18-21 of their mated cycle. Animals chosen for this study were proven fertile regularly cycling monkeys and these were cohabited with males between days 9 and 14 of cycle. Each of the monkeys was exposed to 3 consecutive treatment cycles. During post-treatment phase 2 out of 3 monkeys exposed to males became pregnant. The study clearly demonstrates that it is possible to block normal luteal function as well as luteal rescue of the female monkey by using dghCG in the right dose and mode.

Antifertility effect of tamoxifen as tested in the female bonnet monkey (Macaca radiata).

The administration of a potent antiestrogen, tamoxifen at a dose of 3 mg/kg body weight/day orally post-coitally to cycling mated bonnet monkeys (Macaca radiata) from days 18–30 of cycle resulted in inhibition of establishment of pregnancy in 9 out of 10 monkeys. Tamoxifen effect was not due to interference with luteal function. The effect was specific to tamoxifen as exogenously administered progesterone could not reverse it. In addition to suggesting a role for estrogen in maintenance of early pregnancy in the primate the present study could be a prelude to the development of an effective post-ovulatory approach for regulation of fertility in the human female.