Abstract
Using radioimmunoassay procedures, the levels of plasma, uterine and ovarian prostaglandin (PG) F2α, and those of plasma estradiol and progesterone were measured in intact, hysterectomized or ovariectomized immature female rats pretreated with PMS and subsequent HCG. Occurrenee of ovulation was confirmed at 8 hours after the HCG administration not only in the intact rats but also in the hysterectomized rats.
The levels of plasma estradiol and progesterone, and of uterine and ovarian PGF 2α rose with the PMS injection alone, but they did not reach the peaks before the HCG administration. Both plasma estradiol and uterine PGF2α showed a peak at 2 hours after the HCG injection. These peaks were antecedent 2 or 6 hours before the peaks of ovarian and plasma PGF 2α, respectively. However, such increase of uterine PGF 2α does not seem to be indispensable for ovulation, because ovulation could occur in the hysterectomized rats.
The levels of ovarian PGF 2α showed a high plateau from 4 to 8 hours after the HCG injection, and then rapidly decreased after ovulation.
The levels of plasma PGF 2α peaked not only in the intact rats but also in the hysterectomized rats at 8 hours after the HCG treatment. But in the ovariectomized rats, this plasma PGF 2α peak at 8 hours disappeared and there was no statistical change of plasma PGF 2α throughout the PMS-HCG treatment. Plasma progesterone gradually increased and reached the maximum at 10 hours after the HCG injection.
These results conclude that the main source of increased plasma PGF 2α during the ovulatory process induced with the PMS-HCG treatment is the ovary, and it is strongly suggested that a rapid increase of PGF 2α in the ovary may play some important role (s) in the ovulatory process.
