DIFFERENTIAL EXPRESSION OF CYCLOOXYGENASE-1 AND CYCLOOXYGENASE-2 PROTEINS IN RAT UTERUS AND CERVIX DURING THE ESTROUS-CYCLE, PREGNANCY, LABOR AND IN MYOMETRIAL CELLS

The synthesis of prostaglandins in the uterus at term are modulated by two isoforms of the enzyme cyclooxygenase (COX): constitutive COX-1 a nd inducible COX-2. This study aims to characterize the expression of the protein for COX-1 and -2 in the rat uterus and cervix during the e strous cycle, pregnancy and labor, and in cultured myometrial cells. W estern immunoblotting of proteins was performed and quantitation of pr otein was obtained densitometrically. Results indicate: 1) the rat ute ri, cervix, and isolated myometrial cells express both COX-1 and COX-2 proteins, 2) during pregnancy, both COX-1 and-2 increase, with a dram atic increase at parturition (250%-280%)), 3) a 2-fold increase of cer vical COX-2 is seen at spontaneous labor, 4) during proestrus and estr us, uterine expression of COX-2 is elevated, 5) both COX-1 and -2 were expressed by mt myometrial cells and treatment with IL-1 beta (10 ng/ mL) produced a significant increase in COX-2, and 6) immunocytochemica l studies show that both COX-1 and -2 were primarily localized to the epithelial cells of the endometrium and smooth muscle cells in the cir cular layers of the myometrium in the uterus and to the epithelial cel ls and smooth muscle cells in the cervix. Thus, we propose that increa sed expression of COX-2 may be involved at term in increased uterine c ontractility and cervical ripening.