Can high blood pressure alone increase erythrocytic intracellular sodium concentration?

In order to clarify the direct effects of high blood pressure on erythrocytic intracellular sodium concentration ([Na+]i) and sodium transport systems, a static pressure of 2.5 atm was applied to whole blood in plastic syringes at room temperature for 5 and 24 h. In the control samples, 5 h incubation under atmospheric pressure produced a significant decrease in ouabain-sensitive Na(+)-K+ pump activity and plasma pH, but no change in other parameters. After 24 h incubation, [Na+]i and mean corpuscular volume were significantly increased and intracellular potassium concentration, ouabain-sensitive Na(+)-K+ pump activity, and plasma pH were decreased. The change in [Na+]i during incubation under atmospheric pressure may be due to the increased permeability of the cell membrane and the decrease in ouabain-sensitive Na(+)-K+ pump activity. The pressure load did not increase erythrocytic [Na+]i but did decrease it relative to the control. The pressure load had no apparent effects on sodium transport systems, mean corpuscular volume and pH of plasma relative to the control. Although the mechanisms of the effect of pressure load on [Na+]i were not determined, we did find that high blood pressure alone was unable to increase erythrocytic [Na+]i.