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; HbA(1c), 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.