ObjectivesAlthough the beneficial effects of L-arginine on systemic haemodynamics have been reported in patients with heart failure, its effect on renal function has not been examined. We evaluated the effects of oral administration of L-arginine on renal haemodynamics, sodium and water handling, and various hormonal factors in patients with chronic heart failure.Subjects and methodsA double-blind crossover trial was performed in 17 patients with chronic congestive heart failure (NYHA II–III, 56 ± 12 years of age) who were randomly assigned to receive oral L-arginine (15 g/day) and placebo or placebo and arginine sequentially for 5 days each. Twenty-four hour creatinine clearance (Ccr), and 24-h urinary cyclic guanosine 5-monophosphate (GMP) excretion were determined. Saline loading was performed on day 5 of each treatment. Renal blood flow, glomerular filtration rate (GFR), and urinary sodium excretion rate (UNa) were assessed before and after saline loading.ResultsTwenty-four hour GMP excretion (1.4 ± 1.1 versus 0.8 ± 0.5 μmol/day,P< 0.01) and Ccr (150 ± 43 versus 125 ± 42 ml/min,P< 0.05) were higher and plasma endothelin level (2.5 ± 0.6 versus 3.1 ± 0.8 pg/ml,P< 0.05) was lower with L-arginine treatment compared to placebo treatment. In addition, the relative increase of UNa and GFR after saline loading were significantly higher in L-arginine treatment (UNa, 47 ± 12%; GFR, 44 ± 31%) than in placebo treatment (UNa, 34 ± 9%; GFR, 22 ± 29%) (P< 0.05).ConclusionsOral administration of L-arginine has beneficial effects on glomerular filtration rate, natriuresis, and plasma endothelin level in patients with chronic congestive heart failure.