A Luteolytic Interaction Between Estradiol and Prostaglandin F2α in Hysterectomized Ewes

Abstract

The hypothesis that the luteolytic interaction between prostaglandin F₂α (PGF₂α) and estradiol is independent of the uterus was evaluated in hysterectomized and hysterectomized, ovarian X-irradiated ewes. Hysterectomies and either sham or X-irradiations were performed 7 or 8 days after observation of estrus. After a 72 h recovery period the effects of injections on two consecutive days of: 1) the vehicles for PGF₂α and estradiol benzoate (E₂B), 2) 3.5 mg PGF₂α, 3) 750µ g E₂B, and 4) 3.5 mg PGF₂α + 750 µg E₂B were compared in sham and ovarian X-irradiated ewes. Results of plasma progesterone determinations and mean corpus luteum weights showed that treatment with PGF₂α alone was not luteolytic. Treatment with E₂B alone had marginal effects on corpus luteum function. For example, plasma progesterone concentrations were depressed (P2α and E₂B, complete luteolysis was observed in three of four sham and three of four X-irradiated ewes. These data suggest a luteolytic interaction between estradiol and PGF₂α that is independent of the uterus.