Diuretics and cation transport in hypertensive blacks.

Thiazide diuretics are particularly efficacious in the treatment of hypertension in blacks. A number of observations suggest that many hypertensive blacks have features consistent with a status of "corrected" volume expansion. Our studies, as well as those of other investigators, show that the Na,K pump is inhibited in leucocytes and erythrocytes of blacks with essential hypertension. This observation is also consistent with the concept of volume expansion in hypertensive blacks, since the Na,K pump is inhibited in many forms of experimental volume expansion, including the administration of salt in normal humans. We postulate that the efficacy of thiazide diuretics may be related to their ability to stimulate the Na,K pump. We present data obtained in 13 black hypertensive men in whom Na efflux, and Na,K-ATPase in the erythrocyte rose significantly after 7 days of treatment with hydrochlorothiazide, 50 mg/day. Diuretic therapy may indirectly result in reduced intracellular calcium in the vascular smooth muscle.