EARLY ABORTIFACIENT ACTION OF RU-486 BY CONTINUOUS INTRAVENOUS-INFUSION IN RAT

RU 486 administered through constant intravenous infusion at 20 mg/kg dose on day 8 of pregnancy induced frank vaginal bleeding and resorpti on of all implantations in 100% rats. This was associated with an almo st 4-fold reduction in progesterone secretion rate by the dispersed lu teal cells ex-vivo. At 12 mg/kg dose, an incomplete resorption of impl antations was observed in all treated animals. Results indicate that s low and continuous intravenous infusion of this antiprogestin was high ly effective in terminating pregnancy shortly after implantation in th e rat and this could, at least partially, be related to its luteolytic action in this species.