??1A-Adrenergic receptor polymorphism

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Abstract
The α1-adrenergic receptor (α1-AR) mediates vasoconstriction and plays an important role in the regulation of vascular tone. Increased α1-AR-mediated vasoconstrictor sensitivity, increased vascular reactivity to stress, and an increased prevalence of hypertension occur in African-Americans. The human α1A-AR is the predominant α1-AR subtype in vascular smooth muscle. The potential relevance of α1A-AR genetic variation to ethnic differences in vascular response and to the pathogenesis of hypertension prompted us to determine the frequency distribution of a recently identified polymorphism (Arg492 to Cys) in the α1A-AR in normotensive and hypertensive black and white American individuals. Polymerase chain reaction-based PstI restriction fragment length polymorphisms in the human α1A-AR gene were determined in 231 African-American and 282 Caucasian individuals, both with and without hypertension. There were marked differences in the genotypic and allelic distributions of the Arg492 to Cys α1A-AR polymorphism between African-American and Caucasian individuals (Cys492/Cys492 genotype, normotensive: 7.6% versus 30.1%; hypertensive: 7.1% versus 26.2%; Cys492 allele, normotensive: 29.5% versus 53.8%; hypertensive: 28.8% versus 55.2%; blacks versus whites, P < 0.0001). The frequency of the variant Cys492 allele was similar in normotensive and hypertensive individuals, both in African-Americans (29.5% versus 28.8%) and Caucasians (53.8% versus 55.2%). There were no significant intergenotypic differences in blood pressure (all P > 0.05). The data indicate that this polymorphism is not associated with essential hypertension in black or white Americans, but that the frequency of the α1A-AR Arg492 allele occurs significantly more commonly in African-Americans than in Caucasians. The potential role of the Arg492 to Cys α1A-AR polymorphism in ethnic differences in vascular α1-adrenergic response requires further investigation.

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