PREGNANCY INCREASES OVINE UTERINE ARTERY ENDOTHELIAL CYCLOOXYGENASE-1EXPRESSION

During normal pregnancy, and especially in the third trimester, both u terine blood flow and prostacyclin production by ovine uterine arterie s are dramatically increased. We sought to determine if this is due, i n part, to an increase in cyclooxygenase (COX) expression in the uteri ne artery endothelium. In this study we compared COX expression in ute rine artery endothelium from nonpregnant and third-trimester pregnant (110-142 days' gestation) ewes. COX-2 expression was not detectable by Western blotting in uterine artery endothelium or vascular smooth mus cle (VSM). In contrast, COX-1 expression was clearly observed in uteri ne artery. Immunohistochemical localization of COX-1 was endothelium > VSM, with both cell types showing an increase in COX-1 during the thi rd trimester of pregnancy. COX-1 protein and messenger RNA (mRNA) leve ls were also detectable in collagenase dispersed endothelial cells, wi th expression of COX-1 in uterine artery endothelial cells dramaticall y increased during the third trimester of pregnancy at both the level of protein (346.4 +/- 28% of nonpregnant controls, P < 0.0005) and mRN A (51.04 +/- 7.98-fold of nonpregant controls, P < 0.001). We conclude that the pregnancy induced increases in prostacyclin production by ut erine arteries is largely due to a dramatic increase in expression of COX-1 mRNA and associated protein predominantly occurring in the uteri ne artery endothelium and, to a lesser extent, in the VSM.