Distribution of gap junction protein Connexin 37 in smooth muscle cells ofthe rat trachea and pulmonary artery

Connexin 37, one of the gap junction protein families, has been detected by Northern blotting in various organs and tissues, and found to be especiall y abundant in the lung. However, detailed information on the precise types of cells which express connexin 37 has not been previously published. We th erefore prepared site-specific connexin 37 antibodies and examined the dist ribution of connexin 37 immunohistochemically. Connexin 37 was detected in endothelial cells, in the tunica media of both the pulmonary artery and the aorta, and in the smooth muscle layer of the trachea and bronchioles. In t he tracheal smooth muscle layer, connexin 37 overlapped with desmin-positiv e areas, but was clearly segregated from vimentin- and von Willebrand facto r-positive areas. These results suggest that connexin 37 is expressed in sm ooth muscle cells in the trachea, but not in fibroblastic cells or endothel ial cells. Connexin 37 was partially colocalized with connexin 43 in trache al smooth muscle cells, and showed a gradual increase in expression during postnatal development. To our knowledge, this is the first report to be pub lished regarding the expression of connexin 37 in smooth muscle cells.