Effects of prostaglandin E 1 or E 2 (PGE 1; PGE 2) on luteal function and binding of luteinizing hormone in nonpregnant ewes

Abstract

Two studies were conducted to determine the effects of PGE 1 or PGE 2 on luteal function and binding of luteinizing hormone (LH) to luteal cell membranes in nonpregnant ewes. In Study I, ewes (n=5 per group) received an injection of vehicle (VEH) or 333 μg of PGE 1 or PGE 2 into the tissue surrounding the ovarian vascular pedicle (intrapedicle) on day 7 postestrus. Systemic progesterone concentrations of PGE 1-treated ewes were greater (P<0.01) than those of VEH-treated ewes at 24 and 48 hr after injection. For PGE 2-treated ewes, progesterone concentrations were greater (P<0.01) than for VEH-treated ewes only at 24 hr. Neither PGE 1 nor PGE 2 affected luteal weights or LH binding capacity at 48 hr. Treatment with PGE 1, however, increased (P<0.10) endogenously bound LH at this time. In Study II, ewes (n=5 per group) received an intrapedicle injection of VEH, or 10 mg of PGE 1 or PGE 2 on day 8 postestrus. Systemic progestrone concentrations in PGE 1-treated ewes were less (P<0.01) than for VEH-treated ewes at 24 hr, but by 72 hr were not different from those of VEH-treated ewes. For PGE 2-treated ewes, systemic progesterone declined steadily to reach low values by 72 hr. Prostaglandin E 2 had no effect on luteal binding of LH at 72 hr, whereas PGE 1 increased (P<0.05) LH binding capacity and endogenously bound LH. Although PGE 2 had no apparent effect on luteal binding of LH in these studies, PGE 1 may enhance the function of ovine corpora lutea by stimulating an increase in their binding of LH and capacity to bind LH when the CL receives a luteolytic signal.