1. Erythrocyte sodium, sodium transport (ouabain-sensitive efflux rate of sodium, oMosNa, and ouabain-sensitive efflux rate constant of sodium, oMosNa), sodium-potassium activated ouabain-sensitive adenosine triphosphatase (Na+, K+-ATPase) activity and [3H]ouabain-binding capacity were measured in 15 patients with chronic renal failure and in 10 healthy subjects.
2. As a group, patients with chronic renal failure had a lower erythrocyte sodium and oMosNa compared with healthy subjects.
3. When patients were divided according to their erythrocyte sodium (greater or less than 4 mmol/kg of cells), in the group of patients whose erythrocyte sodium was less than 4 mmol/kg of cells (group A) the oMosNa was higher than that in healthy subjects and the oMosNa, Na+, K+-ATPase activity and [3H]ouabain-binding capacity were the same as those in healthy subjects. In the subgroup of patients with renal failure whose erythrocyte sodium content was greater than 4 mmol/kg of cells (group B) the oMosNa was less and plasma urea concentration higher than in group A and Na+, K+-ATPase activity, [3H]ouabain-binding capacity and oMosNa were lower than in healthy subjects.
4. These results suggest that in early chronic renal failure there is stimulation of ‘sodium pumps’ (without alteration in their number), which causes a lowering of erythrocyte sodium content, and that as the disease progresses there is inhibition of the ‘sodium pumps’ as well as a reduction in membrane permeability so that erythrocyte sodium is near normal.