Association analysis of β2 adrenoceptor polymorphisms with hypertension in a Black African population

Objective To determine whether or not beta(2) adrenoceptor polymorphism is a risk factor for the development: of hypertension in a Black South African population Background Attenuated vasodilator responses to endogenous catecholamines may contribute to the aetiology of hypertension. Downregulation of beta(2) adrenoreceptors (beta(2)AR) following stimulation with agonists is determined in part by variation at the beta(2)AR gene locus. The Glu(27) beta(2)AR genotype results in attenuated downregulation compared with the wild-type Gln(27), receptor, whereas Gly(16) exhibits enhanced downregulation compared to Arg(16). Possible racial differences in the prevalence of the beta(2)AR polymorphisms may be an explanation for the blunted responses to isoprenaline and the increased prevalence of hypertension in Black African populations. Methods One hundred and ninety-two unrelated hypertensives and 123 normotensives of Black South African origin were studied. Hypertensives were recruited from hospital hypertension clinics in the province of Gauteng and if on treatment, had a 2-4 week washout period before 24-h ambulatory blood pressure assessment Normotensive controls were recruited from the same community. Results There was no significant association between either the Arg-Gly(16) polymorphism or the Gln-Glu(27) polymorphism and hypertension status. Furthermore, in the hypertensives, no significant association was seen between beta(2)AR genotype at either site and clinical blood pressure, 24-h blood pressure or left ventricular mass. A significant association was seen between Arg(16) homozygotes and lower body mass index in hypertensives (P=0.007) although this was not a primary end point. Interestingly, the Glu(27) polymorphism was much rarer in this population (allelic frequency 17%) compared to a Caucasian population. Conclusion These data suggest that beta(2)AR polymorphism is not a risk factor for hypertension per se in this defined population. The possibility that the decreased prevalence of Glu(27) in black South African populations explains blunted vasodilator responses to isoprenaline requires further study. J Hypertens 2000, 18:167-172 (C) Lippincott Williams & Wilkins.