Background: Hypercholesterolaemia has been found to impair endothelial function in the systemic and coronary circulations and lipid-lowering therapy with statins has been shown to improve this abnormality.
Methods: We examined the impact of hypercholesterolaemia on L-arginine-induced renal vascular relaxation by a cross-sectional study, and the effects of lipid-lowering therapy by a double-blind, randomized, placebo-controlled study. Using constant infusion input clearance technique (PAH and inulin respectively), changes of renal plasma flow (RPF) and glomerular filtration rate (GFR) in response to intravenous infusions of L-arginine (100 mg/kg/30 min and 500 mg/kg/30 min) were studied in 21 hypercholesterolaemic humans (age 57+/-9 years, LDL-cholesterol 211+/-35 mg/dl) and in 20 young healthy (age 26+/-2 years, LDL-cholesterol 90+/-27 mg/dl) and 20 older healthy age-matched control individuals (age 50+/-8 years, LDL-cholesterol 106+/-20 mg/dl). In addition, changes of blood pressure, heart rate, urinary excretion of sodium, and cyclic guanosine monophosphate were measured. Patients were analysed before and after 3 months treatment with either fluvastatin (40 mg twice daily, n=11) or placebo (n=10).
Results: In hypercholesterolaemic patients, L-arginine increased RPF and GFR (P<0.01) and urinary excretion of sodium (P<0.05) in a dose-dependent manner. Interestingly, changes were similar between the hypercholesterolaemic patients and the young and the age-matched control individuals (DeltaRPF 100 mg/kg/30 min, 40+/-51 ml/min vs 40+/-52 ml/min, P=NS; DeltaRPF 500 mg/kg/30 min, 114+/-85 ml/min vs 130+/-78 ml/min, P=NS). L-arginine significantly lowered systemic arterial pressure and increased heart rate in all groups. Despite significant reductions in LDL-cholesterol levels (291+/-35 mg/dl vs 213+/-30 mg/dl, P<0.001), treatment with fluvastatin did not alter the renal haemodynamic response pattern to L-arginine infusion when compared to baseline values and to those with placebo.
Conclusion: In contrast to studies performed in the vasculature of the human forearm or the coronary circulation, our results suggest that hypercholesterolaemia is not associated with an impaired L-arginine-induced renal vascular relaxation.