Preclinical evaluation of intrauterine progesterone as a contraceptive agent. I. Local contraceptive effects and their reversal
Hudson, R.; Hemphill, P.; Tillson, S.A.
Contraception 17(5): 465-474
1978
ISSN/ISBN: 0010-7824 PMID: 657811 DOI: 10.1016/0010-7824(78)90008-2Document Number: 285259
This study compared the local effects on the rabbit reproductive tract of 10, 65, or 150 mcg of progesterone/day (4.4, 29.6, or 71.4 mcg/day/kg of body weight, respectively), released from a delivery system directly into the uterine lumen. In addition, the reversibility of the effects of progesterone treatment, at a rate of 10 mcg/day, on fertility was evaluated after system removal. Progesterone administered continuously and unilaterally at a rate of 10 mcg/day by intrauterine placement caused greater declines in fertility rations (embryos/corpora lutea) than those observed in animals bearing identical systems that released no hormone. Contralateral horns served as controls. Fertility reduction was greater for both placebo systems and progesterone systems (10 mcg/day) when placed in the upper 1/3 of the uterus than in the lower 1/3. After placebo and progesterone systems were removed, all groups rapidly regained their fertility. Embryonic mortality in all groups during treatment was comparable to that in control horns of animals unilaterally pregnant. Progestational effects were observed only in the treated horn at the lowest hormone release rate (10 mcg/day); with the higher doses, however, the endometrium of both horns was affected. Ovulation did occur during all treatment in all animals, except those receiving the highest dose, 150 mcg/day. The importance of both a localized placement effect and a localized progestational effect on contraceptive action was confirmed; however there was no effect on the ovulatory process from intrauterine progesterone delivered at a contraceptive dose.