Effect of indomethacin, an inhibitor of prostaglandin biosynthesis on the length of pseudopregnancy in rats and hamsters.

Abstract

Pseudopregnancy (PSP) in rats was significantly lengthened after subcutaneous administration of 0.2-1.0 mg indomethacin/day, starting on day 5 of PSP. Injections of 1 mg indomethacin on days 5 and 6 or days 7 and 8, as well as a single injection of 2 mg indomethacin on day 6, also produced a significant increase of the duration of PSP. In hamsters, doses of 300-500 mug indomethacin per day starting on day 5 of PSP did not alter the length of PSP, but a significant prolongation varying from 11 to more than 30 days was observed after a treatment with 1 mg of indomethacin daily. It was further observed that the ovaries of hamsters autopsied on day 31 of PSP were very small and the uteri resembled those of ovariectomized animals. It is concluded that indomethacin lengthens pseudopregnancy in both rats and hamsters and that the latter species showed a more variable response. It seems that chronic administration of indomethacin in hamsters caused a long-lasting suppression of ovarian hormone production.