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

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... DESIGN AND METHODS -Twenty-three elderly patients with type 2 diabetes (age, 65 Ϯ 6 years; HbA 1c , 7.8 Ϯ 1.6%) with coexisting arterial hypertension (158 Ϯ 19/83 Ϯ 11 mmHg) and elevated cholesterol levels (total cholesterol, 215 Ϯ 33 mg/dl) were examined. These patients were compared with a young and healthy reference group (n ϭ 20; age, 26 Ϯ 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 paminohippurate and inulin, respectively. RESULTS -L-Arginine infusion similarly influenced renal hemodynamics in patients and reference subjects: RPF increased by 7 Ϯ 11 and 7 Ϯ 11% in diabetic and reference subjects, respectively (P ϭ NS). Other parameters of renal hemodynamics such as glomerular filtration rate (5 Ϯ 5 vs. 4 Ϯ 4%) and filtration fraction (Ϫ1 Ϯ 8 vs. Ϫ1 Ϯ 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. Abbreviations: GFR, glomerular filtration rate; RPF, renal plasma flow. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.