Changes in concentrations of prostaglandins and sex steroids around the time of induced ovulation in prepuberal gilts.

Abstract

Prepuberal gilts were injected intramuscularly with human chorionic gonadotropin (HCG)(6 IU/kg of body weight) 72 hr after receiving pregnant mare serum gonadotropin (PMS) (12 IU/kg of body weight) and ovulation was verified by laparotomy. Changes in concentrations of prostaglandins (PGs) and steroids in peripheral plasma, ovarian vein plasma and follicular fluid were examined. Ovulation occurred 32 to 48 hr after HCG administration. Progesterone levels were low at the time of HCG administration, but markedly increased after ovulation. Estradiol-17β and testosterone levels which reached maximum values 72 hr after PMS administration, decreased after HCG administration and remained low until about 36 hr after ovulation. Levels of PGF2α in ovarian vein reached maximum values near the time of ovulation. Concentrations of PGE1, PGF2α and 6-keto-PGF1α in follicular fluid remained relatively low until 18 hr after HCG injection followed by an increase 36 to 42 hr after HCG administration and reached maximum values as expected time of ovulation approached. In gilts given indomethacin 24 hr after HCG injection, ovulation was inhibited in a dose-dependent manner. But patterns of steroid secretion in indomethacin-treated gilts were similar to those of controls. Levels of PGE1 and PGF2α in the follicular fluid were low 48 and 72 hr after HCG injection. These results suggest that PGs play an important role in process of ovulation in gilts as well as in other animals.