Endothelial ANP/GC-A signaling is critically involved in acute ANP-induced stimulation of natriuresis

Question: Cardiac atrial (ANP) and B-type natriuretic peptide (BNP) are centrally involved in maintaining blood pressure by regulating vascular tone, endothelial permeability and renal sodium/water excretion. These physiological effects are mediated by the membrane-bound guanylate cyclase-A (GC-A). Despite the clear relevance of NP-signaling for kidney function, it is unclear which cell types mediate these effects and if renal microvessels play a role. Methods: To identify renal target cells of NPs we performed systematical expression analysis of NP receptors in mouse kidneys using mRNA in-situ hybridization. The results led us to investigate the function of isolated perfused kidneys from mice with tamoxifen-induced endothelium-restricted deletion of GC-A (Cdh5-Cre/GC-Aflox/flox). Results: In mouse kidneys, podocytes and intrarenal blood vessels express GC-A at high abundance, while no expression was detectable in the tubular system. In the renal medulla, marked expression of GC-A was found in endothelial cells of peritubular capillaries. Infusion of ANP induced a concentration-dependent increase in diuresis, natriuresis and renal blood flow in isolated perfused kidneys. Endothelium-restricted knockout of GC-A reduced total renal GC-A expression by approximately 50% and abolished the natriuretic response to 100 pM ANP, while enhancing the ANP-induced increase in renal blood flow. In addition, the kidneys of knockout mice have a higher weight and lower mRNA expression of genes associated with endothelial barrier function. Conclusion: Endothelial GC-A signaling is critically involved in the ANP-induced increase in natriuresis and diuresis. The surprising finding that endothelial GC-A deletion prevents diuretic while augmenting vasodilating ANP effects directs our ongoing studies.