ERYTHROCYTE ION-TRANSPORT AS INDICATOR OF SENSITIVITY TO ANTIHYPERTENSIVE DRUGS

Multiple ion transport defects have been characterized in red blood ce ll membranes from essential hypertensive patients. These seem to be bi ochemical markers of at least three different types of essential hyper tension. A first type is characterized by low pump, low cotransport fl uxes in erythrocytes. These hypertensive patients are apparently ident ical to the salt-sensitive, low-renin hypertensive patients, in whom l ow pump and cotransport seem to result from the presence of circulatin g endogenous ouabainlike and bumetanide-like factors. These hypertensi ve patients are sensitive to diuretic drugs and to vase-relaxants with salidiuretic activity, as expected from a reduction in plasma volume and circulating levels of endogenous ion transport inhibitors. A secon d type of essential hypertension is characterized by increased red cel l Na+:Li+ countertransport and [Na+, K+, Cl-] cotransport. These hyper tensive patients tend to present normal or high plasma renin activity, disorders in lipid metabolism, and left ventricular hypertrophy. Hype rtensive patients belonging to this group seem to be resistant to diur etic drugs but sensitive to vasorelaxants. A third type of essential h ypertension is characterized by both high membrane sodium leak and hig h [Na+, K+, Cl-] cotransport in erythrocytes. Hypertensive patients in this group are resistant to diuretics, angiotensin-converting enzyme (ACE) inhibitors, calcium antagonists, and centrally acting drugs.