Alterations in calcium-handling of erythrocytes in spontaneously hypertensive rats. Calcium-induced changes in the osmotic fragility of erythrocytes in hypertension.

To investigate the sensitivity to calcium of erythrocytes in hypertension, changes in the osmotic fragility of erythrocytes following Ca-loading were observed. Washed erythrocytes were obtained from spontaneously hypertensive rats (SHR, Okamoto and Aoki) and age-matched normotensive Wistar Kyoto rats (WKY). Treatment of erythrocytes with Ca-ionophore A23187 and Ca in the medium caused a reduction in the osmotic fragility which correlated with the Ca-concentration. The degree of alteration in the osmotic fragility of erythrocytes was greater in SHR than in WKY. Oral administration of hydralazine to SHR significantly reduced the blood pressure. However, the alterations in the osmotic fragility of erythrocytes secondary to Ca-loading were not different between hydralazine-treated and untreated SHR. In the presence of a Ca-antagonist (verapamil or diltiazem) in the medium, the reduction of the osmotic fragility of erythrocytes caused by Ca-loading was inhibited, and the differences between SHR and WKY were abolished by Ca-antagonists. These results suggest that the greater changes in osmotic fragility of erythrocytes caused by Ca-loading in SHR could be due to a genetic abnormality of Ca-handling by the cell membranes, and that this abnormality might cause an increase in intracellular Ca, which contributes, in part, to the pathogenesis of hypertension.