Secretion of prostaglandins (PG) E2 and PGF2α by the bovine endometrium and the effects of oxytocin (OT) on these secretions during the estrous cycle were investigated. Bovine uteri were classified into five luteal stages (early I: Days 2-3; early II: Days 5-7; mid-: Days 8-12; late: Days 15-17; regressed: Days 19-21). After 1 h of pre-incubation, endometrial tissues (20-30 mg) were exposed to 0 or 100 nM OT for 4 h. PGE2 concentration in the medium was higher than that of PGF2α during the luteal phase, and declined at the regressed luteal stage (P<0.05). In contrast, PGF2α secretion reached the highest value at the regressed luteal stage (P<0.05). OT significantly stimulated both PGE2 and PGF2α secretion at the early luteal stage (P<0.05). Although OT enhanced PGF2α secretion at the late and regressed luteal stages (P<0.05), PGE2 secretion was reduced by OT at the same time (P<0.05). These results indicate that there are significant differences in the pattern of PGE2 and PGF2α secretion by the bovine endometrium during the estrous cycle and suggest that OT may play a role in modulating the secretion of PGE2 as well as PGF2α.
1998 Society for Reproduction and Development