Calmodulin-dependent Ca2+ transport across plasma membranes in primary hypertension.

The rate of calcium transport in the erythrocytes in both forms of primary hypertension [essential hypertension (EH) of humans and spontaneously hypertensive rats (SHR)] and in microsomes of SHR brain were studied. In the erythrocyte membranes subjected to calmodulin depletion by EGTA treatment both the affinity of the Ca-pump for Ca2+ and its maximal activity in primary hypertension did not differ from normotensive controls. The addition of exogenous calmodulin to calmodulin-stripped membranes from erythrocytes of EH or SHR and microsomes of SHR brain resulted in a smaller increase of the Ca-pump activity. It is suggested that the decrease of the rate of calmodulin-dependent calcium transport across the plasma membrane may be a cause for the increased intracellular calcium content found in some tissues in primary hypertension.