Dose and time dependent luteotropic and luteolytic action of prostaglandin F2α in the luteinized rabbit ovary

The mechanism of stimulatory and inhibitory action of PGF_2α on ovarian steroidogenesis both under and conditions has been studied in the pseudo-pregnant rabbits. Short term incubation of the ovaries with PGF_2α (2.82 × 10⁻⁵M) resulted in an increased synthesis of progesterone and 20α-OH P. The addition of PGF_2α in the medium and further incubation of the ovaries obtained from rabbits that had been constantly infused with PGF_2α (0.5 μg/min.) for two hours resulted in increased synthesis of these progestins. The ratio of progesterone to 20α -OH P was also enhanced under these conditions and thus supported the luteotropic action of small doses of PGF_2α under short term incubations. However, as the amount of PGF_2α infused was increased to 5 μg/min., the addition of PGF_2α under conditions strikingly decreased the production of these progestins. The ratio of progesterone to 20α -OH P was also decreased and thus was indicative of luteolytic action of higher doses of PGF_2α. High doses of PGF_2α (5.64 × 10⁻⁴M) failed to I cause any significant change in the progestin synthesis under short term incubation. These results thus suggest that the luteotropic and luteolytic action of PGF_2α in the luteinized rabbit ovary is dose and time dependent.