GAP-JUNCTIONS IN HUMAN UMBILICAL-CORD ENDOTHELIAL-CELLS CONTAIN MULTIPLE CONNEXINS

We investigated the expression pattern of gap junctional proteins (con nexins, Cx) in situ and in vitro and their functional characteristics in cultured human umbilical vein endothelial cells (HUVEC) and culture d human umbilical artery endothelial cells (HUAEC). In both arteries a nd veins, Cx37, Cx40, and Cx43 could be detected in situ and in vitro (passages 2-4). Distribution patterns of Cx40 and Cx43 were homogeneou s in situ but more heterogeneous in vitro. Cx37 is heterogeneously exp ressed both in situ and in vitro. Among most cells, no Cx37 staining c ould be detected; when present, it was found as bright spots between s ome clusters of cells. Cx40 was more abundant in cultured arterial end othelium than in cultured venous endothelium. Dye-coupling experiments with Lucifer yellow CH revealed extensive dye spread in HUVEC (15.2 /- 0.4, mean +/- SE, n = 110) but was significantly restricted in HUAE C (9.8 +/- 0.3, n = 110). Electrophysiological gap junctional characte ristics were determined in cultured HUVEC and HUAEC pairs by use of th e dual voltage-clamp technique. In contrast to the dye-coupling experi ments, mean macroscopic electrical conductance was significantly large r for HUAEC pairs (31.4 +/- 6.0 nS, n = 12) than for HUVEC pairs (16.6 +/- 2.8, n = 18). In HUVEC, we measured multiple single gap junctiona l channel conductances in the range of 19-75 pS. Interestingly, additi onal conductances of 80-200 pS were measured in HUAEC, possibly partia lly reflecting activity of channels formed of Cx40, which are more abu ndant in the cultured arterial endothelial cells.