Abstract
The hypothesis that the luteolytic interaction between prostaglandin F/sub 2/..cap alpha..(PGF/sub 2/..cap alpha..) 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 PGF/sub 2/..cap alpha.. and estradiol benzoate (E/sub 2/B), (2) 3.5 mg PGF/sub 2/..cap alpha.., (3) 750 ..mu..g E/sub 2/B, and (4) 3.5 mg PGF/sub 2/..cap alpha.. + 750 ..mu..g E/sub 2/B were compared in sham and ovarian x-irradiated ewes. Results of plasma progesterone determinations and mean corpus luteum weights showed that treatment with PGF/sub 2/..cap alpha.. alone was not luteolytic. Treatment with E/sub 2/B alone had marginal effects on corpus luteum function. For example, plasma progesterone concentrations were depressed (P < 0.05) when compared to vehicle treated controls at isolated times between 60 and 96 h after the first injection in both sham and x-irradiated ewes, and the mean corpus luteum weight for the x-irradiated group was less than that found for the control groups (P < 0.05). However, following treatment with both PGF/sub 2/..capmore » alpha.. and E/sub 2/B, 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 PGF/sub 2/..cap alpha.. that is independent of the uterus. In a second experiment, hysterectomized sham and x-irradiated ewes were treated with 7.0 mg PGF/sub 2/..cap alpha... Plasma progesterone determinations and corpus luteum weights suggested that complete luteolysis was observed in all sham-irradiated ewes and in two of four x-irradiated ewes. This dose of PGF/sub 2/..cap alpha.. also proved to be effective in three of four x-irradiated, uterine intact ewes. These results suggest that ovarian follicles are not an absolute requirement for PGF/sub 2/..cap alpha..-induced luteolysis.« less
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