EXPRESSION OF CYCLOOXYGENASE-1 AND CYCLOOXYGENASE-2 IN-OVINE ENDOMETRIUM DURING THE ESTROUS-CYCLE AND EARLY-PREGNANCY

In this study we investigated the expression of the two cyclooxygenase s, cox-1 and -2, in sheep uterine tissues during the estrous cycle and early pregnancy. We identified the cox-2 isoform in the ovine uterus by Western blot and demonstrated that the two cyclooxygenases exhibite d different patterns of expression. Cox-1 was expressed at steady stat e levels in the endometrium during the estrous cycle and comparable st ages of pregnancy. In contrast, cox-2 was highly and transiently expre ssed from days 12-15 of the estrous cycle and declined thereafter to u ndetectable levels. Endometrium from early pregnant ewes showed a simi lar pattern of cox-2 expression, although there was a slower decrease beyond day 15. Immunohistochemical studies demonstrated that cox-1 was localized in both epithelial and stromal cells, whereas cox-2 was loc alized solely in the luminal epithelium and to a lesser extent in the superficial glands. Treatment of ovariectomized ewes with steroids ind icated that expression of cox-1 remained at constant levels whatever t he treatment. In contrast, endometrial cox-2 was highly induced by a 1 0-day progesterone treatment. Estradiol slightly increased cox-2 expre ssion but only after progesterone priming. Collectively these results suggest that the developing ability of the uterus to synthesize PGs is due to the induction of cox-2.