Accumulation of thromboxane B2 within periovulatory ovine follicles: relationship to adhesion of platelets to endothelium.

Levels of thromboxane (TX) B2 (the stable metabolite of TXA2) were quantified by radioimmunoassay in periovulatory ovine follicles. Follicles were obtained before, and at 8, 16, 24 and 32 h after the onset of the preovulatory surge in secretion of luteinizing hormone (the ovulatory event culminates at approximately 24 h). Unruptured follicles were segregated into tissue and fluid components. A portion of the wall of each follicle was processed for examination by high resolution light and transmission electron microscopy. Concentrations of TXB2 in homogenates of the follicular wall, and in fluid of follicles that had not yet ruptured, were dramatically elevated at 24 h. Aggregates of platelets (the suspected source of TXA2) were adhered to endothelial cells at this time; in some cases intra and extravascular clotting was apparent. It is suggested that platelets and(or) TXA2 might contribute to periovulatory processes in the ewe.