Multiple connexins localized to individual gap-junctional plaques in humanmyometrial smooth muscle

The synchronous contractions of the uterus in labour depend on electrical c oupling of myometrial smooth muscle cells by gap junctions. In the human my ometrium, gap junctions are scarce in the non-pregnant uterus, but become a bundant at term in preparation for labour. We have previously demonstrated that in the human myometrium at term, three different gap-junctional protei ns are expressed, connexins 43, 45, and 40. These connexins are known to ha ve distinctive functional capacities in in vitro expression systems but whe ther, in the human myometrium in vivo, they are coassembled into the same g ap junction or form different types of gap junction has previously been unc lear. By applying triple immunogold labelling to sections of Lowicryl-embed ded tissue for electron microscopy, together with complementary immunoconfo cal microscopy, we demonstrate here that connexins 43, 45, and 40 are commo nly present as mixtures within the same gap-junctional plaque. While all ga p junctions contain connexin43, the relative signal for each connexin type varies between individual junctions. The presence within single gap-junctio nal plaques of three different connexins, each with the potential for confe rring distinctive channel properties, suggests an inherent versatility for modulation of smooth muscle cell intercellular communication properties dur ing human parturition. (C) 2001 Wiley-Liss, Inc.