Tempol Augments the Blunted Cutaneous Microvascular Thermal Reactivity in Healthy Young African Americans

Abstract

African Americans (AA) have a higher risk for a variety of cardiovascular and metabolic diseases including hypertension, stroke, peripheral artery disease, and type 2 diabetes mellitus when compared with Caucasian Americans (CA). While this elevated risk is multifactorial impaired vascular endothelial function is a contributing factor. In this study, we hypothesized that cutaneous hyperemic response to a standard local heating protocol is reduced in young AA when compared with CA. We further hypothesized that tempol (a superoxide dismutase mimetic) would increase this cutaneous vasodilatory response to local heating in AA. Microdialysis fibers were randomly assigned to receive 1) lactated Ringer's solution (Control), 2) 10 mM ascorbic acid, or 3) 10 μM 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (Tempol) at a rate of 2.0 μl/min. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux divided by mean arterial pressure. All CVC data were presented as a percentage of maximal CVC (%CVCmax) that was determined by maximal cutaneous vasodilation induced by 44 °C plus sodium nitroprusside administration. Twenty‐four (12 AA, 12 CA) young (23 ± 4 years of age) and healthy (body mass index (24.3 ± 2.8 kg/m2) subjects participated in the study. At the Control site, there were no differences between groups for baseline %CVCmax during resting without heat (P = 0.275). During 33 °C, there were still no differences in %CVCmax between groups (P = 0.107); however, %CVCmax at 39 °C was lower in AA when compared with CA (P < 0.001). At the ascorbic acid site, there were no differences between groups for both baseline %CVCmax during resting without heat (P = 0.549) and %CVCmax during 33 °C (P = 0.120); however, %CVCmax at 39 °C was attenuated in AA relative to CA (P < 0.001). At tempol site, there were no differences between groups for all phases including baseline CVC during resting without heat (P = 0.791), %CVCmax during 33 °C (P = 0.550), and %CVCmax at 39 °C (P = 0.948). These data suggest that 1) cutaneous vasodilation in response to local heating is blunted in AA relative to CA. 2) in AA, elevated O2− generation attenuates cutaneous vasodilation when heat is directly applied to the skin.Support or Funding InformationInstitutional start‐up funds from The University of Texas at Austin