Calmodulin Distribution and Ca2+ Transport in the Erythrocytes of Patients with Essential Hypertension

Abstract

The rate of Ca transport and calmodulin distribution in the erythrocytes of patients with essential hypertension were studied. In erythrocyte membranes subjected to calmodulin depletion by treatment with EGTA [ethylene glycol bis(.beta.-aminoethyl ether)N,N,N'',N''-tetraacetic acid], both the affinity of the Ca pump for Ca2+ and its maximal activity were the same in normotensive and hypertensive patients. The addition of exogenous calmodulin to calmodulin-stripped membranes from erythrocytes of patients with essential hypertension resulted in a smaller increase of the maximal activity of the Ca pump and its affinity for Ca2+. The addition of calmodulin to erythrocyte membranes obtained without EGTA treatment resulted in a smaller increase of the maximal activity of the Ca pump only. There were no significant differences of calmodulin distribution (cytoplasmic concentration and size of the membrane-bound pool) between the erythrocytes of normotensive and hypertensive patients. Alterations in the Ca pump activity of the erythrocyte membranes of patients with essential hypertension are probably related to the alteration of interaction between calmodulin and Mg2+, Ca2+-ATPase.