[Potassium, sodium and magnesium content of plasma-free erythrocyte sediment and of average individual erythrocytes determined by means of a 51 CR-EDTA isotope dilution method]

[Sodium-potassium-adenosine triphosphatase-activity in red cell ghosts of patients with essential hypertension (author's transl)]

Increased sodium concentration and high influx of Na22 are reported in erythrocytes of patients with essential hypertension. It was speculated, that these findings are due to a disturbed transport for sodium across red cell membranes. We found a significantly increased activity of the ouabainsensitive Na-K-ATP'ase in red cell ghosts of 27 patients with essential hypertension compaired with 32 normotensive controls. There existed no difference in Mg-ATP'ase-activity between the two groups. These findings suggest an increased activity of the Na-pump in red cell membranes of patients with essential hypertension.

[Influence of beta 1-methyl-digoxin to red cell electrolyte contents in healthy normals (author's transl)]

6 healthy controls received daily doses of 0.6 mg beta-methyl-digoxin for 3 days and further 0.3 mg for the following 5 days each. After the first 3 days sodium content in the red cells increased from 4.8 to 6.6 meg/kg significantly in parallel to the glycoside level of 1.5 ng/ml (1.2 times 10-9 M). At the same time magnesium in the cells fell significantly from 4.1 to 3.7 meg/kg. There was no change in the concentration of potassium, calcium or chloride at this time. While the glycoside level dropped during the following 5 days under 0.3 mg of methyl-digoxin to 1.2 ng/ml (1 times 10-9 M), sodium content in the cells increased further up to 8.3 meq/kg and was paralleled by a decrease in potassium content from 84.6 to 82.0 meq/kg. There were no changes in plasma electrolyte concentrations during the experiments. Our results confirm the concept of Hoffman that there are two transport pathways in human red cells which differ basically in their dependencies of the sodium and potassium composition of the external medium and the concentration of glycoside needed to inhibit the transport. Our data evidence that red cell electrolyte contents reflect levels of digoxin. They might be useful to follow up the therapeutical effect of cardiac glycosides.