[Action of prostaglandin F2 alpha on pregnancy in mice. Prevention of its abortive property by progesterone].

Prostaglandin F2alpha determines a high proportion of abortions in the mouse when administered before implantation at a dose level of 2 mg/kg. After implantation between days 6-8 or 7-9, doses 20 times higher are necessary to produce the effect. Daily progesterone administration, 5 mg per animal, from day 1 to day 17 allow the evolution of pregnancy in 60% of the mice even when 120 mg/kg prostaglandin is given. This dose determines usually 100% abortions. No teratogenic effect has been observed.