Abstract
An increase in Ca-content of erythrocytes can induce the characteristic changes, such as reduced osmotic fragility and increased rigidity of the membrane. These phenomena are induced by the binding of the intracellular Ca to the cytoskeleton proteins (contractile proteins) distributed in the erythrocyte membrane.
To investigate the Ca-sensitivity of the erythrocyte membrane, the changes of the osmotic fragility of erythrocytes by Ca-loading were observed. Samples from essential hypertension (WHO I and II) and spontaneously hypertensive rats (SHR, Okamoto & Aoki) were examined in comparison with age-matched normotensive subjects and Wistar Kyoto rats (WKY), respectively. Treatment of washed erythrocytes with Ca-ionophore (A 23187) and Ca in the bathing medium caused the reduction of the osmotic fragility dose-dependently on Ca-concentration. The degree in alteration of the osmotic fragility by Ca-loading was significantly greater in hypertension than normotensive controls. However, in the presence of Ca-antagonists (verapamil, diltiazem) or calmodulin antagonist (trifluoperazine) in the medium, the reduction of the osmotic fragility by Ca-loading was inhibited, and the differences between the hypertensives and the controls were abolished by Ca-antagonists and a calmodulin antagonist.
These results suggest that greater changes of the osmotic fragility of erythrocytes by Ca-loading in hypertension might be due to a genetic abnormality of the Ca-handling of the cell membranes, and it would be corrected by Ca-inhibitors.
