Functional gene testing of the Glu298Asp polymorphism of the endothelial NO synthase

Objectives To test whether the Glu298Asp polymorphism of the endothelial nitric oxide synthase (eNOS) gene is of functional relevance in humans by altering endothelium-dependent vasodilation, Background The Asp298 variant of the eNOS gene product has been associated with arterial hypertension, coronary artery disease and myocardial infarction. The pathogenetic mechanism has not yet been elucidated, Since endothelium-dependent vasodilation has been shown to be impaired in these disorders, we hypothesized that the Glu298Asp polymorphism of the eNOS gene influences endothelium-dependent vasodilation, Methods In 80 patients with normal or elevated cholesterol, endothelium-dependent and -independent vasodilation was assessed. Forearm blood flow was measured by plethysmography in response to intra-arterial (i.a.) infusion of 12 and 48 mug/min acetylcholine and 3.2 and 12.8 mug/min nitroprusside, respectively. N-G-monomethyl-L-arginine (L-NMMA) in doses of 4, 8 and 16 mu mol/min was infused to test basal nitric oxide (NO) production and release. Genomic DNA was extracted from brood samples to determine the Glu298Asp polymorphism of the eNOS gene at position 1917 GTT after BanII restriction. Results Baseline parameters (age, gender, blood pressure, body mass index, cholesterol level) were similar across the genotypes, Genotype frequencies did not deviate from the Hardy-Weinberg equilibrium. No differences in forearm brood flow to i.a, acetylcholine (average increase: + 554 +/- 371%), nitroprusside or L-NMMA infusion were found across the eNOS genotypes, neither for endothelium-dependent or endothelium-independent vasodilation, nor for basal NO production and release, Our sample size of n = 80 had a power of > 80% (beta = 0.20) with a P value < 0.05 (<alpha> = 0.05) to detect a 200% difference in forearm brood flow response to 48 mug/min acetylcholine. Conclusions At a power of 80%, we can exclude a relevant effect on endothelium-dependent vasodilation due to the eNOS Glu298Asp polymorphism. Thus, our functional genetic study does not suggest any biological effect of the eNOS Glu298Asp genotype on the cardiovascular system via an influence on endothelium-dependent vasodilation. (C) 2000 Lippincott Williams & Wilkins.