CONNEXIN-43 AND CONNEXIN-40 GAP JUNCTIONAL PROTEINS ARE PRESENT IN ARTERIOLAR SMOOTH-MUSCLE AND ENDOTHELIUM IN-VIVO

The distributions of connexin 43 (Cx43) and connexin 40 (Cx40) in smoo th muscle and endothelium of resistance vessels were examined using in direct immunofluorescence techniques coupled with confocal microscopy. Cx43 and Cx40 were found in smooth muscle and endothelium. Similar st aining patterns were found in microvessel samples from brain and crema ster of the rat and from arterioles of the hamster cheek pouch. Double -labeling studies showed a high degree of colocalization of Cx40 with Cx43, suggesting the presence of multiple connexins within a single ju nctional plaque. Quantitative comparisons were made of the fluorescent patterns in the endothelium and smooth muscle of rat brain arterioles . Cx43 and Cx40 plaque diameters were 0.9 +/- 0.1 and 0.8 +/- 0.1 (SE) mu m, respectively, in the endothelial layer and 0.5 +/- 0.1 and 0.5 +/- 0.1 mu m, respectively, in the smooth muscle. There was no differe nce between mean plaque diameters of Cx43 and Cx40 in endothelium or s mooth muscle. However, plaques were significantly larger in endotheliu m than in smooth muscle (P < 0.05). These findings demonstrate the pot ential for cell-cell communication in both cell types of the wall of a rterioles from three different tissues. The data also suggest a greate r level of coupling within the endothelium.