Effect of indomethacin on the vascular architecture of preovulatory ovine follicles: possible implication in the luteinized unruptured follicle syndrome.

Ovarian follicles sometimes fail to rupture and accumulate large quantities of fluid, yet undergo luteinization and form a steroidogenically competent luteal structure, the luteinized unruptured follicle syndrome. This condition can be mimicked in mammals by administration of indomethacin, an inhibitor of biosynthesis of prostaglandins. Blockade of ovulation by this drug is exerted at the follicular level. Ovulatory failure in sheep given a single intramuscular injection of indomethacin after induction of a surge of of luteinizing hormone was associated with follicular hyperemia as assessed by scanning electron microscopic examination of microcorrosion vascular casts and light microscopic quantification of follicular vascular space. The apical stigma of control (ovulatory) follicles was ischemic. The luteinized unruptured follicle syndrome appears to be the consequence of a chronic follicular inflammatory-like reaction involving inhibition of synthesis of prostaglandins.