cGMP-dependent protein kinase is present in high concentrations in contractile cells of the kidney vasculature.

There is increasing evidence that the recently discovered Atrial Natriuretic Factor, a potent vasorelaxing, natriuretic and diuretic hormone, may achieve some of its diverse physiological effects by regulating the cellular level of cGMP. Since activation of a cGMP-dependent protein kinase is an established effect of cGMP, we have studied the cellular localization of cGMP-dependent protein kinase within the rat kidney cortex using both immunocytochemical and immunochemical procedures. cGMP-dependent protein kinase is selectively concentrated in contractile cells of the kidney vasculature, including both intra- and extraglomerular mesangial cells, vascular smooth muscle cells and microvascular pericytes, as well as in interstitial myofibroblasts. cGMP-dependent protein kinase is not detectable in significant amounts in tubular epithelial cells, podocytes, or endothelial cells. These results support the hypothesis that Atrial Natriuretic Factor may achieve some, and maybe all, of its renal effects by regulating hemodynamic parameters via activation of cGMP-dependent protein kinase within vascular contractile cells.