Quantification of Ca(2+)-ATPase in erythrocytes from subjects with essential hypertension or Raynaud's phenomenon.

The increased peripheral vascular resistance in subjects with essential hypertension and in subjects with primary Raynaud's phenomenon is thought to be the consequence of an impaired control of intracellular Ca2+ in vascular smooth muscle cells. Abnormal membrane handling of Ca2+ in human essential hypertension is not limited to vascular smooth muscle cells but has been demonstrated in a number of blood cells, for example, erythrocytes. Ca(2+)-ATPase activity and Ca(2+)-ATPase densities were measured in erythrocyte membranes from healthy volunteers and subjects with essential hypertension or with Raynaud's phenomenon. We found no significant differences between the three groups in the Ca(2+)-ATPase activity and in the number of Ca(2+)-ATPase immunoreactive sites per erythrocyte. Furthermore, we could not demonstrate any influence of sex or age on these two parameters. We conclude that, in essential hypertension and in Raynaud's phenomenon, the Ca2+ extrusion capacity of the erythrocytes is not altered.