An ultrastructural study of preovulatory apical development in mouse ovarian follicles: effects of indomethacin.

The effects of the prostaglandin synthesis inhibitor, indomethacin, on the preovulatory morphology of apical follicle walls have been examined by transmission electron microscopy. Immature mice, superovulated with 5 IU pregnant mare serum (PMS) followed 40 hours later by 80 IU luteinizing hormone (LH) were treated with either 10 mg/kg indomethacin or an equivalent volume of the indomethacin vehicle 10 minutes prior to LH. Follicular apices from both groups were compared at 12 hours post-LH. Indomethacin treatment suppressed many of the morphological changes normally occurring in the apex during preovulatory development. Whereas apices from vehicle-treated animals demonstrated marked deterioration, dissociation, and thinning of tissue, the cell layers of apices from indomethacin-treated animals remained thickened and tightly packed, with limited signs of disruption. The results presented herein are consistent with the idea that prostaglandins are essential mediators of ovulation and suggest that these lipids augment apical rupture by mobilizing granulosa cells and stimulating the loss of connective tissue elements.