l-Arginine-Induced Vasodilation of the Renal Vasculature Is Not Altered in Hypertensive Patients With Type 2 Diabetes

Abstract

OBJECTIVE—Diabetes, arterial hypertension, hypercholesterolemia, and aging are associated with endothelial dysfunction in various vasculatures. Endothelium-dependent vasodilation of the renal vasculature cannot be easily assessed, but infusion of l-arginine, the substrate of endothelial nitric oxide synthase, leads to an increase in renal plasma flow (RPF) in humans. We have examined the effect of l-arginine infusion on renal hemodynamics in hypertensive patients with type 2 diabetes. RESEARCH DESIGN AND METHODS—Twenty-three elderly patients with type 2 diabetes (age, 65 ± 6 years; HbA1c, 7.8 ± 1.6%) with coexisting arterial hypertension (158 ± 19/83 ± 11 mmHg) and elevated cholesterol levels (total cholesterol, 215 ± 33 mg/dl) were examined. These patients were compared with a young and healthy reference group (n = 20; age, 26 ± 2 years). The effect of l-arginine infusion (100 mg/kg over 30 min) on RPF and glomerular filtration rate were measured using the constant input clearance technique with p-aminohippurate and inulin, respectively. RESULTS—l-Arginine infusion similarly influenced renal hemodynamics in patients and reference subjects: RPF increased by 7 ± 11 and 7 ± 11% in diabetic and reference subjects, respectively (P = NS). Other parameters of renal hemodynamics such as glomerular filtration rate (5 ± 5 vs. 4 ± 4%) and filtration fraction (−1 ± 8 vs. −1 ± 9%) were not significantly different between diabetic and reference subjects, too. CONCLUSIONS—l-Arginine-induced vasodilation of the renal vasculature is not different between a group of hypertensive diabetic patients and a young, healthy reference group. These data were obtained using low-dose l-arginine infusion.