The differential expression of myometrial connexin-43, cyclooxygenase-1 and -2, and G(s)alpha proteins in the upper and lower segments of the human uterus during pregnancy and labor

There is evidence from many studies indicating that a number of specific qu iescent and contractile associated proteins are temporally regulated in the myometrium during pregnancy. In this present investigation we provide data that strongly suggest that myometrial connexin-43, cyclooxygenase-l and 2 (COX-1 and -2), and G(s)alpha proteins are also spatially expressed within the human uterus during pregnancy and labor. Using paired lower and upper s egment myometrial samples taken from individual women at term and during sp ontaneous labor, we have measured the expression of these proteins by immun oblotting with specific antibodies. We report that the myometrial gap junct ion connexin-43 protein is expressed at much greater levels in the upper ut erine compared to the lower uterine segment and that this difference is eve n more pronounced during the course of labor. Conversely, myometrial COX-1 and -2 proteins appear to be expressed at much greater levels in the lower compared to the upper uterine segment. Moreover, the level of expression of both proteins is unaffected by the onset of parturition. In contrast, myom etrial G(s)alpha protein appears to be uniformly expressed in both lower an d upper segments and is similarly down-regulated during parturition, as pre viously reported. The differential expression of COX-1 and -2 and connexin- 43 in the uterus may allow cervical ripening before and dilatation during l abor and facilitate effective propagation of contractions from fundus to ce rvix, which may be further facilitated by the down-regulation of G(s)alpha at the onset of parturition.