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Blunted Endothelial Dependent Vasodilation in the Cutaneous Microvasculature of College‐Aged African Americans
Author(s) -
Patik Jordan C,
Hurr Chansol,
Christmas Kevin M.,
Brothers R. Matthew
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.952.2
Subject(s) - vasodilation , medicine , microdialysis , forearm , brachial artery , endocrinology , acetylcholine , provocation test , blood pressure , surgery , pathology , alternative medicine , central nervous system
African Americans (AA) have elevated risk for hypertension, insulin resistance, and cardiovascular disease compared to their Caucasian American (CA) counterparts. Previously, we have observed attenuated vasodilation in the cutaneous vasculature during local heating in young, healthy AA compared to CA. Impaired endothelium‐dependent vasodilation in response to acetylcholine (ACh) is present in other at‐risk populations, including aging, obesity, smokers, and hypercholesterolemics. Therefore, the aim of the current study was to test the hypothesis that AA have a blunted vasodilatory response to the ACh analog methacholine (MCh). Twenty‐three (12 AA, 11 CA) volunteers free of overt disease participated in the study. AA and CA groups were matched for age (21.5±1 vs 23.9±1 years, P=0.30), BMI (25±1 vs 23.8±1, P=0.31), and sex (AA: 6M/6F, CA:6M/5F). MCh was delivered via a sterile microdialysis fiber inserted in the dermal layer of the left forearm. MCh doses of 10 −6 , 10 −5 , 10 −4 , 10 −3 , 10 −2 , and 1M (mixed in lactated Ringer's) were infused into the skin for 6 min each dose at a rate of 2μL/min. Cutaneous red blood cell flux was measured via laser Doppler fluximetry (LDF) continuously and averaged over the last min of each dose. Local heaters were set to 33°C throughout the dose‐response protocol. Brachial blood pressure was taken during the last min of each dose on the contralateral arm. Cutaneous vascular conductance (CVC) at each dose was calculated as LDF/MAP and then normalized to each individual's maximal CVC during combined 44° heating and 28mM sodium nitroprusside infusion (CVCmax). Using normalized data, four parameter logistic dose response curves for each group were compared with an extra sum of squares F‐test with maximum constrained to 100 (%CVCmax). Including all parameters, AA and CA dose response curves were different (P<0.001). Log EC 50 for AA was at a higher dose (−2.814±0.26) compared to CA (−4.434±0.19, P<0.001). Hillslope was not different between groups (P=0.33). Baseline values were also not different (AA: 10.37±5.26 %CVCmax vs CA: 15.02±4.27 %CVCmax, P=0.54). The results of this study indicate that a significantly greater dose of MCh is required to reach 50% of maximal vasodilation in healthy, young AA compared to CA. This pharmacological evidence supports earlier findings suggestive of impaired endothelium‐dependent microvascular function in AA. Support or Funding Information Institutional Start‐up funds from the University of Texas at Austin