Sodium transport and red cell deformability.

Inhibition of the Na-K pump by a circulating factor is thought to be of importance in the pathophysiology of essential hypertension. We tested the correlation between an inhibition of the Na-K pump by digoxin and the deformability of red blood cells (RBC) both in vitro and in vivo. Erythrocytes were incubated with digoxin (0-1.3 mumol/l) for 1 h at 37 degrees C. Highest concentration of digoxin (0.13 and 1.3 mumol/l) significantly diminished Na-K pump activity, measured by uptake of 86rubidium (Rb). There was a parallel decrease in red cell filtrability. In nine healthy volunteers, intake of digoxin (0.2 mg b.i.d.) over a 5-day period did not alter red cell deformability and uptake of 86Rb. Taken together, inhibition of the Na-K pump in vitro correlates with a reduced red cell deformability. However, this occurs at a toxic dosis of digoxin.