Differences in vascular nitric oxide and endothelium-derived hyperpolarizing factor bioavailability in blacks and whites

Arterioscler Thromb Vasc Biol. 2014 Jun;34(6):1320-7. doi: 10.1161/ATVBAHA.113.303136. Epub 2014 Mar 27.


Objective: Abnormalities in nitric oxide (NO) bioavailability have been reported in blacks. Whether there are differences in endothelium-derived hyperpolarizing factor (EDHF) in addition to NO between blacks and whites and how these affect physiological vasodilation remain unknown. We hypothesized that the bioavailability of vascular NO and EDHF, at rest and with pharmacological and physiological vasodilation, varies between whites and blacks.

Approach and results: In 74 white and 86 black subjects without known cardiovascular disease risk factors, forearm blood flow was measured using plethysmography at rest and during inhibition of NO with N(G)-monomethyl-L-arginine and of K(+) Ca channels (EDHF) with tetraethylammonium. The reduction in resting forearm blood flow was greater with N(G)-monomethyl-L-arginine (P=0.019) and similar with tetraethylammonium in whites compared with blacks. Vasodilation with bradykinin, acetylcholine, and sodium nitroprusside was lower in blacks compared with whites (all P<0.0001). Inhibition with N(G)-monomethyl-L-arginine was greater in whites compared with blacks with bradykinin, acetylcholine, and exercise. Inhibition with tetraethylammonium was lower in blacks with bradykinin, but greater during exercise and with acetylcholine.

Conclusions: The contribution to both resting and stimulus-mediated vasodilator tone of NO is greater in whites compared with blacks. EDHF partly compensates for the reduced NO release in exercise and acetylcholine-mediated vasodilation in blacks. Preserved EDHF but reduced NO bioavailability and sensitivity characterizes the vasculature in healthy blacks.

Clinical trial registration url: http://clinicaltrials.gov/. Unique identifier: NCT00166166.

Keywords: African Americans; EDHF; exercise; nitric oxide; vasodilation.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Adult
  • Biological Availability
  • Biological Factors / physiology*
  • Black or African American
  • Bradykinin / pharmacology
  • Exercise
  • Female
  • Forearm / blood supply
  • Humans
  • Male
  • Middle Aged
  • Nitric Oxide / physiology*
  • Nitroprusside / pharmacology
  • Potassium Channels, Calcium-Activated / physiology
  • Tetraethylammonium Compounds / pharmacology
  • Vascular Resistance / drug effects
  • Vasodilation / drug effects
  • Vasodilation / physiology*
  • White People
  • omega-N-Methylarginine / pharmacology


  • Biological Factors
  • Potassium Channels, Calcium-Activated
  • Tetraethylammonium Compounds
  • endothelium-dependent hyperpolarization factor
  • Nitroprusside
  • omega-N-Methylarginine
  • Nitric Oxide
  • Acetylcholine
  • Bradykinin

Associated data

  • ClinicalTrials.gov/NCT00166166