The purpose of the present study was to examine alterations in membrane fluidity of erythrocytes in
essential hypertension by means of an electron paramagnetic resonance (EPR) and a spin labeling method. In addition, we investigated the effects of
ouabain on the fluidity of erythrocytes, and elucidated a possible role of Na+, K(+)-
ATPase in the regulation of membrane fluidity in
hypertension. Erythrocytes obtained from patients with
essential hypertension were examined compared with those from age-matched normotensive subjects. The EPR spectra for 5-nitroxide
stearate incorporated into erythrocyte membranes were studied. The values of the outer hyperfine splitting and order parameter (S) of the EPR spectra were significantly higher in patients with
essential hypertension than in normotensive subjects. This finding shows that the membrane fluidity of erythrocytes might be lower in
essential hypertension.
Ouabain-loading of erythrocytes decreased the membrane fluidity (S value was increased). The
ouabain-induced changes were significantly greater in
essential hypertension than in normotensive subjects. These results demonstrate that the membrane fluidity of erythrocytes might be lower in
essential hypertension than in normotensive subjects. Furthermore, the membrane fluidity might be highly dependent on the Na+, K(+)-
ATPase activity in
essential hypertension, which would suggest an abnormality in Na(+)-related cellular functions in
hypertension.