BACKGROUND - A common polymorphism of the beta(1)-adrenergic receptor Arg389Gly markedly affects function in vitro, but little is known about its in vivo significance.
METHODS AND RESULTS - Resting and exercise hemodynamic responses were measured in subjects homozygous for Arg389 (n = 21) or Gly389 (n = 13) alleles before and 3 hours after administration of a beta-blocker, atenolol. Demographic characteristics and atenolol concentrations were similar in the two genotypic groups. Genotype had a marked effect on resting hemodynamic responses to atenolol, with Arg389-homozygous subjects having a larger decrease in resting systolic blood pressure (8.7 +/- 1.3 mm Hg versus 0.2 +/- 1.7 mm Hg, P < .001) and mean arterial blood pressure (7.2 +/- 1.0 mm Hg versus 2.0 +/- 1.7 mm Hg, P = .009). Attenuation of exercise-induced hemodynamic responses by atenolol was not affected by genotype.
CONCLUSIONS - There is reduced sensitivity of Gly389 homozygotes to a beta-adrenergic receptor antagonist, and this polymorphism may be an important determinant of variability in response to beta-blockade.