Pathophysiology of hypertension in blacks. The pathophysiology of hypertension in the black population differs to some extent from that of the nonblack population. Although black hypertensives exhibit enhanced sodium retention, expanded plasma volume, lower plasma renin activity, and a greater increase in blood pressure in response to high levels of Na+ intake compared with nonblack hypertensives, there is considerable heterogeneity in these studies. Alterations in ion transport mechanisms, such as a decrease in Na+K(+)-ATPase activity and Na+K+ cotransport, have been demonstrated in the black hypertensive population. Those features provide the physiologic basis for the differential response to monotherapy with diuretics and, perhaps, with calcium channel blockers, that is observed in black hypertensives, particularly when compared with responses to beta-blockers or angiotensin converting enzyme inhibitors. 