Effects of prostacyclin on ovulation and microvasculature of the in vitro perfused rabbit ovary

Prostacyclin (prostaglandin I₂) methyl ester at 0.1, 1, or 10 μg/ml was added to the perfusate of one rabbit ovary every 2 hours for the first 10 hours of perfusion. The contralateral ovary was perfused with medium alone. Prostacyclin methyl ester at 1 and 10 μg/ml induced ovulation in the absence of gonadotropin, with ovulatory efficiencies of 26.7% ± 3.8% and 46.5% ± 5.0%, respectively. Most ovulated ova (77.4%) did not progress beyond the germinal vesicle stage, and there was no significant degeneration of ovulated ova or follicular oocytes. Examination of the follicular microvasculature 5 hours after exposure to prostacyclin revealed marked vessel dilatation and filling defects at the apex. By 7 hours after prostacyclin exposure, the intrafollicular space contained extravasated resin, reflecting increased vascular permeability. The vascular changes paralleled those previously observed in gonadotropin-induced ovulation. These results indicate that prostacyclin acting locally alters the vascular integrity of the follicle wall and facilitates follicle rupture.