Prostaglandin E 1 : studies on antifertility and luteolytic effects in hamsters and rats.

Abstract

Prostaglandin (PC) E1 was administered to hamsters and rats to study its effects on pregnancy, egg transport, decidual cell reaction, implantation process and parturition. The effects on pregnancy differed markedly between the two species. In hamsters, a daily dose of 300 µg (approx 2.5 mg/kg) for 3 days between days 4 and 9, terminated pregnancy. In rats, on the other hand, even sublethal doses (7 mg/kg) when given twice daily from days 4 to 7 of pregnancy, did not exert antifertility effects, but the treatment reduced the number and size of implantation sites. The antifertility doses of PGE1 in hamsters decreased peripheral plasma progesterone levels, caused atrophy of corpora lutea and inhibited development of deciduomata; both pregnancy and decidual growth could be maintained by simultaneous administration of exogenous progesterone. These findings imply that PGE1 exerts luteolytic effects in hamsters despite its known vasodilator properties. When administered during the tubal sojourn of zygotes, PGE1 inhibited implantation process, as studied by the Pontamine blue reaction in rats, and reduced the size and number of implants; otherwise, however, embryos appeared normal, suggesting occurrence of delayed implantation of blastocysts. Such effects were not observed in hamsters. Injection of PGE1 into near term hamsters induced premature littering of pups.