β2-adrenergic receptor polymorphisms at codon 16, cardiovascular phenotypes and essential hypertension in whites and African Americans

beta(2)-Adrenergic receptors (beta(2)-AR) contribute to cardiovascular regulation by influencing several functions and previous studies suggest that a decreased function of the beta(2)-AR may be involved in essential hypertension. beta(2)-AR are polymorphic and certain polymorphisms of these receptors are of functional importance. We focus here on the Arg(16)-->Gly(16) beta(2)-AR polymorphism, which shows enhanced agonist-promoted downregulation of the receptor and which, in two recent studies, yielded opposite results in terms of association with essential hypertension: an increased frequency of the Gly(16) variant in African-Caribbean hypertensives and of the Arg(16) variant in offspring of Norwegian white hypertensive parents. In the current study, we genotyped 243 subjects, including both African-American and white individuals, for codon 16 polymorphism and assessed blood pressure and cardiovascular function using impedance cardiography and presser sensitivity to phenylephrine. We found similar patterns of cardiovascular function and expression of hypertension with the two genotypes of codon 16. There was no statistically significant difference in the overall allelic distribution of the two genotypes: among African-Americans, 51% of the hypertensives and 50% of the normotensives carried the Arg(16) allele, whereas among the white subjects 40% of the hypertensives and 47% of the normotensives were carriers of the Arg(16) allele. Although we observed a statistically significant increase in the Arg(16)/Gly(16) heterozygotes in the African-American population, the Gly(16) allele was not significantly increased in the AfricanAmericans compared to whites. These findings indicate that the codon 16 polymorphisms are not associated with hypertension in a mixed American study population nor do they appear to substantially impact on a variety of hemodynamic variables. Am J Hypertens 2000;13:1021-1026 (C) 2000 American Journal of Hypertension, Ltd.