Tempol augments the blunted cutaneous microvascular thermal reactivity in healthy young African Americans

Abstract

African Americans (AA) have elevated risk for cardiovascular disease relative to other populations. We hypothesized that cutaneous hyperemic response to local heating is reduced in young AA relative to CA and this is due to elevated oxidative stress. As such, ascorbic acid (a global antioxidant) and tempol (a superoxide dismutase mimetic) would improve this response in AA. Microdialysis fibers received (1) lactated Ringer's (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⁻¹. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure. Data were presented as a percentage of maximal CVC (%CVCmax) induced by 44°C heating plus sodium nitroprusside. Twenty-four (12 AA, 12 CA) young (23 ± 4 yrs) subjects participated. During 39°C heating %CVCmax was lower in AA at Control (CA: 65 ± 20 % vs. AA: 47 ± 15 %; P < 0.05) and Ascorbic Acid (CA: 73 ± 14 % vs. AA: 49 ± 17 %; P < 0.01). At Tempol site, there were no differences between groups. This was followed by infusion of 10 mm Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) at all sites to assess nitric oxide (NO) contribution to vasodilation during local heating. The NO contribution was lower in AA relative to CA at 39°C; however, this was restored with Tempol. These data suggest that: (1) cutaneous vasodilation to local heating is blunted in AA relative to CA. (2) elevated O₂⁻ generation attenuates NO-mediated cutaneous vasodilation in AA.

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