Effects of the nitric oxide synthase inhibitor ronopterin (VAS203) on renal function in healthy volunteers

Aims: Reduced nitric oxide (NO) availability may adversely affect renal perfusion and glomerular filtration. The aim of the present study was to characterize in detail the pharmacological effects of VAS203, an inhibitor of NO Synthase, on renal haemodynamics in humans.

Methods: This double-blind, randomized, placebo-controlled, cross-over phase-I-study comprised 18 healthy men. Renal haemodynamics were assessed with constant-infusion input-clearance technique with p-aminohippurate and inulin for renal plasma flow (RPF) and glomerular filtration rate (GFR), respectively. After baseline measurement, a constant infusion of the tetrahydrobiopterin analogue ronopterin (VAS203, total 10 mg/kg body weight) or placebo was administered at random order for 6 hours additionally. After a wash-out phase of 28 days, the second course was applied. In parallel, markers of early kidney injury and renal function were assessed repeatedly up to 48 hours after starting VAS203/placebo-infusion.

Results: VAS203-infusion resulted in a significant decrease of RPF (P < .0001) and GFR (P < .001) compared to placebo, but magnitude was within the physiological range. RPF and GFR recovered partly 2 hours after end of VAS203-infusion and was normal at beginning of the second infusion period. Compared to placebo, preglomerular resistance (P < .0001), and to lesser extent postglomerular resistance (P < .0001) increased, resulting in a decrease of intraglomerular pressure (P < .01). No treatment related effect on markers of early kidney injury, and on renal function (P for all >.20) have been observed.

Conclusions: Our phase-I-study in healthy humans indicates that VAS203 (10 mg/kg body weight) reduces renal perfusion and glomerular function within the physiological range mainly due to vasoconstriction at the preglomerular site.

VAS203; glomerular filtration rate; nitric oxide synthase; renal haemodynamics; renal plasma flow.