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

Area of Science:

• Cardiovascular Physiology
• Vascular Biology
• Racial Differences in Health

Background:

• Previous studies suggest abnormalities in nitric oxide (NO) bioavailability in Black populations.
• The role of endothelium-derived hyperpolarizing factor (EDHF) and its interplay with NO in vasodilation between racial groups remains unclear.
• This study investigates potential differences in NO and EDHF bioavailability and their impact on physiological vasodilation in healthy Black and White individuals.

Purpose of the Study:

• To determine if differences exist in nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) bioavailability between Black and White individuals.
• To assess how these potential differences affect resting and stimulus-mediated vasodilation.
• To test the hypothesis that vascular NO and EDHF bioavailability varies between racial groups at rest and during pharmacological and physiological vasodilation.

Main Methods:

• Plethysmography was used to measure forearm blood flow in 74 White and 86 Black subjects.
• Nitric oxide (NO) bioavailability was inhibited using N(G)-monomethyl-L-arginine.
• Endothelium-derived hyperpolarizing factor (EDHF) was inhibited using tetraethylammonium to block K(+) Ca channels.
• Vasodilation was assessed at rest and during stimulation with bradykinin, acetylcholine, sodium nitroprusside, and exercise.

Main Results:

• Resting forearm blood flow reduction was greater with NO inhibition in White subjects compared to Black subjects.
• Overall vasodilation in response to bradykinin, acetylcholine, and sodium nitroprusside was lower in Black subjects than in White subjects.
• NO inhibition significantly impacted vasodilation more in White subjects during bradykinin, acetylcholine, and exercise challenges.
• EDHF inhibition showed lower impact in Black subjects with bradykinin but higher impact during exercise and acetylcholine challenges.

Conclusions:

• The contribution of nitric oxide (NO) to resting and stimulus-mediated vasodilator tone is greater in White individuals compared to Black individuals.
• Endothelium-derived hyperpolarizing factor (EDHF) plays a compensatory role for reduced NO bioavailability during exercise and acetylcholine-mediated vasodilation in Black individuals.
• Healthy Black individuals exhibit preserved EDHF function alongside reduced NO bioavailability and sensitivity, characterizing their vascular physiology.