ABSTRACT
AIM: Natriuretic peptides, BNP and ANP increase renal blood flow in experimental animals. The signalling pathway in human kidney vasculature is unknown. It was hypothesized that BNP and ANP cause endothelium-independent relaxation of human intrarenal arteries by vascular natriuretic peptide receptor-A, but not -B and -C, which is mimicked by agonists of soluble guanylyl cyclase sGC. METHODS: Human (n = 54, diameter: 665 ± 29 µm 95% CI) and control murine intrarenal arteries (n = 83, diameter 300 ± 6 µm 95% CI) were dissected and used for force recording by four-channel wire myography. Arterial segments were pre-contracted, then subjected to increasing concentrations of BNP, ANP, phosphodiesterase 5-inhibitor sildenafil, sGC-activator BAY 60-2770 and -stimulator BAY 41-2272. Endothelial nitric oxide synthase (eNOS) dependence was examined by use of L-NAME and eNOS knockout respectively. Molecular targets (NPR A-C, sGC, phosphodiesterase-5 and neprilysin) were mapped by PCR, immunohistochemistry and RNAscope. RESULTS: BNP, ANP, sildenafil, sGC-activation and -stimulation caused concentration-dependent relaxation of human and murine intrarenal arteries. BNP responses were independent of eNOS and were not potentiated by low concentration of phosphodiesterase-5-inhibitor, sGC-stimulator or NPR-C blocker. PCR showed NPR-A and C, phosphodiesterase-5, neprilysin and sGC mRNA in renal arteries. NPR-A mRNA and protein was observed in vascular smooth muscle and endothelial cells in arteries, podocytes, Bowmans capsule and vasa recta. NPR-C was observed in tubules, glomeruli and vasculature. CONCLUSION: Activation of transmembrane NPR-A and soluble guanylyl cyclase relax human preglomerular arteries similarly to phosphodiestase-5 inhibition. The human renal arterial bed relaxes in response to cGMP pathway.
