Prostaglandin E-1 or E-2 (PGE(1), PGE(2)) prevents premature luteolysis induced by progesterone given early in the estrous cycle in ewes

摘要

The objective of this study was to determine whether prostaglandin E-1 (PGE(1)) or prostaglandin E-2 (PGE(2)) prevents premature luteolysis in ewes when progesterone is given during the first 6 days of the estrous cycle. Progesterone (3 mg in oil, im) given twice daily from Days 1 to 6 (estrus = Day 0) in ewes decreased (P < 0.05) luteal weights on Day 10 postestrus. Plasma progesterone concentrations differed (P < 0.05) among the treatment groups; toward the end of the experimental period, concentrations in jugular venous blood decreased (P < 0.05) compared with the other treatment groups. Plasma progesterone concentrations in ewes receiving PGE(1) or PGE(1) + progesterone were greater (P < 0.05) than in vehicle controls or in ewes receiving PGE(2) or PGE(2) or PGE(2) + progesterone. Chronic intrauterine treatment with PGE(1) or PGE(2) prevented (P < 0.05) decreases in plasma progesterone concentrations, luteal weights, and the proportion of luteal unoccupied and occupied LH receptors on Day 10 postestrus in ewes given exogenous progesterone, but did not affect (P > 0.05) concentrations of PGF(2 alpha) in inferior vena cava blood. Progesterone given on Days 1 to 6 in ewes advanced (P < 0.05) increases in PGF(2 alpha) in inferior vena cava blood. We concluded that PGE(1) or PGE(2) prevented progesterone-induced premature luteolysis by suppressing loss of luteal LH receptors (both unoccupied and occupied)