Mechanisms of Elevated Cutaneous Vascular Tone in College-Aged Black Individuals.

Background: Hypertension prevalence is greatest in the US non-Hispanic Black population, possibly through reduced vascular function. Although heightened cutaneous vascular tone and vasoconstrictor responsiveness have been reported in Black individuals, the underlying physiological mechanisms remain unknown.

Methods: Thirteen Black (6 women, 22±2 years) and 10 non-Hispanic White (4 women, 25±4 years) participants underwent intradermal perfusion of norepinephrine alone (10^-8 to 10^-2 M; control) or coinfused with ascorbic acid (general antioxidant), L-NAME (N^ω-nitro- L-arginine methyl ester; a nitric oxide synthase inhibitor), or combined ascorbic acid and l-NAME. Cutaneous vascular conductance was used to estimate vascular tone.

Results: Non-Hispanic Black participants had lower absolute conductance at the control (P=0.012), but not ascorbic acid or l-NAME sites (both P>0.123). Black participants also had lower absolute baseline conductance at all sites (0.26±0.13 versus 0.37±0.14 flux/mm Hg) and across the norepinephrine perfusions (≈51% lower; both P<0.05). At baseline and across norepinephrine perfusions, ascorbic acid increased absolute conductance compared with control in both groups (Black: +94%; White: +39%), while l-NAME reduced absolute conductance in the White participants only (-43%; all P<0.05). Across all doses, control relative conductance was not different between the groups (P>0.05), though the ascorbic acid and combined sites in the Black participants and all sites in the White participants produced greater relative conductance than control (all P<0.05).

Conclusions: These data suggest greater tonic, but not norepinephrine-induced, cutaneous vasoconstriction in Black individuals, which appears to be mediated by greater oxidative stress contributing to reduced nitric oxide bioavailability.