Heterogeneous localization of connexin40 in the renal vasculature

The renal circulation, which treats 25% of the cardiac output, is organized and regulated in unique patterns. Gap junction channels may contribute to the control of vascular tone by transmitting intracellular signals rapidly between cells of the blood vessel. We investigated the distribution patterns of the major vascular gap junction proteins in the murine kidney by immunofluorescence staining of frozen sections, and connexin40 (Cx40) was the most prominent connexin detected. The endothelial cells of large vessels within the kidney consistently showed abundant Cx40 immunoreactivity, but small vessels showed unique distributions of Cx40 along their courses within the kidney. Cx40 immunoreactivity between endothelial cells was abundant in the interlobular arteries and the proximal portion of the afferent arterioles, but was significantly decreased when arterioles approached the glomerulus. No Cx40 immunoreactivity was detected in the region of the glomerular isthmus where the afferent and efferent arterioles join the glomeruli, although glomeruli showed very intense patchy staining for Cx40. Intense patchy staining for Cx40 was also found in the modified smooth muscle cells of the juxtaglomerular apparatus, but none was detected in smooth muscle cells elsewhere in the vasculature. Taken together, these data suggest that the abundance of Cx40-containing gap junctions may be important for coordinating function of cells within individual blood vessels, while their absence in juxtaglomerular regions of the arterioles may prevent conduction of signals between the glomerulus and afferent or efferent arterioles.