Red Blood Cell Na⁺-Transport, Na-K-ATPase and Phosphate Ester Metabolism in Essential Hypertension

Abstract

Much evidence suggests that essential hypertension is partly due to an increase in the circulating concentration of an inhibitor of Na-K-ATPase by increasing vascular smooth muscle sodium concentration, thereby inducing changes that lead to a rise in peripheral vascular resistance. In essential hypertension, red blood cells (RBC) have been used as a model for cells in general to demonstrate the existence of this inhibitor. Findings on RBC Na⁺ concentration, Na⁺ transport and Na-K-ATPase, however, are controversial and may be attributed to different methodologies applied for measurements. The objective of the present study was to evaluate whether the conflicting data might depend on a variable removal of a Na-K-ATPase inhibiting factor due to different preparation procedures of the biological material prior to determination of biochemical parameters. Therefore, we measured intracellular concentrations of Na⁺ and K⁺ inorganic phosphate (P_i) ouabain-sensitive Na⁺ transport, Na-K-cotransport, total and ouabain-sensitive p_i release of freshly drawn RBCs and finally Na-K-ATPase activity of haemolysed and dialysed RBCs and of haemoglobin-free RBC-membranes.