title: Blacks have a greater sensitivity to α1-adrenoceptor-mediated venoconstriction compared with whites.
abstract: Blacks have increased hemodynamic responses to both physiological and pharmacological adrenergic stimulation compared with whites, and this may contribute to the greater prevalence of hypertension in this ethnic group. A small study suggested enhanced α1-adrenoreceptor-mediated arterial vasoconstriction in the forearm vasculature of blacks compared with whites, but it is unknown whether this reflects a generalized vascular phenomenon. The objective of this study was to examine the hypothesis that there are ethnic differences in venous α1-adrenoreceptor responsiveness. Using a linear variable differential transformer, we measured local dorsal hand vein responses to increasing doses of the selective α1-adrenoreceptor agonist, phenylephrine, in 106 subjects (64 whites and 42 blacks). There was wide interindividual variability in responses to phenylephrine. The dose that produced 50% of maximal constriction (ED50) ranged from 11 to 5442 ng/min, and maximal venoconstriction (Emax) ranged from 13.5% to 100%. Blacks (geometric mean ED50 =172 ng/min; 95% confidence interval, 115-256 ng/min) were more sensitive to phenylephrine than whites (310 ng/min; 95% confidence interval, 222-434 ng/min; unadjusted P=0.026; adjusted P=0.003). Median Emax was slightly higher in blacks (89%; interquartile range, 82% to 98%) compared with whites (85%; interquartile range, 75% to 95%; P=0.07). Taken together with previous findings in arterial vessels, our results suggest a generalized increased sensitivity to α1-adrenoreceptor-mediated vasoconstriction in blacks. Increased vascular α-adrenoreceptor sensitivity could predispose to hypertension, and future studies addressing the contribution of this mechanism to ethnic differences in the prevalence of hypertension will be of interest.
authors: Departments of Medicine and Pharmacology, Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors: Abiodun
authors: A
authors: Adefurin
authors: Laxmi V
authors: LV
authors: Ghimire
authors: Utkarsh
authors: U
authors: Kohli
authors: Mordechai
authors: M
authors: Muszkat
authors: Gbenga G
authors: GG
authors: Sofowora
authors: Sachin Y
authors: SY
authors: Paranjape
authors: C Michael
authors: CM
authors: Stein
authors: Daniel
authors: D
authors: Kurnik
mesh_terms: D000293:Adolescent; D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology*; D000328:Adult; D044383:Black People; D005260:Female; D006225:Hand / Q000098:blood supply; D006801:Humans; D006973:Hypertension / Q000208:ethnology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010656:Phenylephrine / Q000494:pharmacology; D015995:Prevalence; D012016:Reference Values; D014481:United States / Q000453:epidemiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014680:Veins / Q000187:drug effects / Q000502:physiology*; D044465:White People; D055815:Young Adult; D001741:Black or African American
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D010656:Phenylephrine
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