Effect of treatment of estrous ewes with indomethacin on the distribution of ovarian blood to the periovulatory follicle.

The level of prostaglandin (PG) F2 alpha increases within the wall of the ovine follicle pending ovulation. Coincidently, the quantity of ovarian blood distributed to the follicular wall progressively declines. A potential cause(PGF2 alpha)-and-effect (impaired follicular blood supply) relationship was considered. At an early stage of estrus, ewes were injected systemically either with vehicle or indomethacin (an inhibitor of biosynthesis of prostaglandins). Abdominal laparotomies were carried out and the ovaries examined near the expected time of ovulation. The ovary containing the largest follicle or an ovulation point was perfused with radioactive microspheres via the ovarian artery. The periovulatory follicle was isolated from the ovary and the content of radioactivity monitored with respect to that of the whole ovary. Follicular tissue was analyzed for PGF2 alpha. Treatment with the drug was associated with: 1) failure of follicular rupture; 2) follicular hyperemia and edema; and 3) suppressed synthesis of PGF2 alpha. A reduction of the supply of ovarian blood reaching the preovulatory follicle, and a mediatory task of follicular prostaglandins in this process, could be a critical determinant of ovulation.