Background--Endothelial dysfunction because of reduced nitric oxide bioavailability is a key feature of essential hypertension. We have found that normotensive siblings of subjects with essential hypertension have impaired endothelial function accompanied by altered arginine metabolism.

Methods and Results--We have identified a novel C/T polymorphism in the 3'UTR of the principal arginine transporter, solute carrier family 7 (cationic amino acid transporter, y+ system), member 1 gene (SLC7A1). The minor T allele significantly attenuates reporter gene expression (P<0.01) and is impaired in its capacity to form DNA-protein complexes (P<0.05). In 278 hypertensive subjects the frequency of the T allele was 13.3% compared with 7.6% in 498 normotensive subjects (P<0.001). Moreover, the overall genotype distribution observed in hypertensives differed significantly from that in normotensives (P<0.001). To complement these studies, we generated an endothelial-specific transgenic mouse overexpressing L-arginine transporter SLC7A1. The Slc7A1 transgenic mice exhibited significantly enhanced responses to the endothelium-dependent vasodilator acetylcholine (-log EC₅₀ for wild-type versus Slc7A1 transgenic: 6.87±0.10 versus 7.56±0.13; P<0.001). This was accompanied by elevated production of nitric oxide by isolated aortic endothelial cells.

Conclusions--The present study identifies a key, functionally active polymorphism in the 3'UTR of SLC7A1. As such, this polymorphism may account for the apparent link between altered endothelial function, L-arginine, and nitric oxide metabolism and predisposition to essential hypertension.