The role of nitric oxide in the regulation of glomerular haemodynamics in humans

Abstract

Background. According to experimental data, the afferent glomerular arteriole is particularly under control of nitric oxide (NO). By use of pharmacological manoeuvres, we examined whether this finding holds true in the human renal circulation in vivo. Methods. Seventy-seven volunteers (aged 50±9 years) with mild to moderate essential hypertension (n = 57) or arterial normotension (n = 20) were examined. Basal NO activity in the renal circulation was assessed by the change of renal plasma flow (RPF) through systemic infusion of the NO synthase inhibitor, N^G-monomethyl-l-arginine (l-NMMA; 4.25 mg/kg). Hypertensive patients were treated over 8 weeks with either the calcium-channel blocker amlodipine or the AT₁-receptor blocker valsartan, primarily dilating the afferent and efferent arteriole, respectively. Subsequently, renal haemodynamics and NO activity in the renal circulation were determined again. Results.l-NMMA reduced RPF in normotensive (by 57±70 ml/min/1.73 m²; P2; Pr = 0.39, P2; (P2; (PConclusions. NO plays an important role in the regulation of human glomerular haemodynamics, probably with a greater contribution to afferent than to efferent arteriolar tone in man.