Mineralocorticoid exposure and receptor activity modulate microvascular endothelial function in African Americans with and without hypertension

Prior work suggests blood pressure in African Americans is more sensitive to the effects of aldosterone than in Caucasians. This mechanism may relate to a negative response of the vascular endothelium to aldosterone, including reduced glucose-6-phosphate dehydrogenase (G6PD) activity. Thirty-three African Americans (11 hypertensives, 22 controls) without evidence of diabetes or metabolic syndrome completed the protocol. The protocol included measurement of in vivo microvascular endothelial function by digital pulse arterial tonometry and ex vivo measurement of endothelial function by videomicroscopy of arterioles obtained from these same subjects with and without exposure to aldosterone or spironolactone. Systemic and arteriolar G6PD activities were also measured. In vivo and ex vivo microvascular endothelial function were impaired in African Americans with hypertension. One-hour exposure with aldosterone impaired endothelium-dependent vasodilation in arterioles from normotensive subjects, while 1 hour of spironolactone exposure reversed endothelial dysfunction in arterioles from hypertensive subjects. G6PD activity was impaired in hypertensive arterioles. Aldosterone-related endothelial dysfunction may be responsible for at least a portion of the greater blood pressure sensitivity to aldosterone in African Americans. This may be in part related to vascular suppression of G6PD activity.