1.Ouabain-sensitive ATPase (adenosine triphosphatase) activity was measured in the erythrocyte membranes of twenty patients with chronic renal disease. Decreased activity was found in nineteen of the twenty patients. The average decrease was 38%.2. In three patients erythrocyte sodium concentration exceeded 9.5 mmol/l of RBC and these patients had the most marked decreases in ouabain-sensitive ATPase activity.3. By contrast, in only two of 100 patients admitted to a general medical ward was erythrocyte sodium concentration greater than 9.5 mmol/l of RBC.4.Ouabain-insensitive and calcium-activated components of erythrocyte membrane ATPase were unaffected by chronic renal disease.

The ouabain-sensitive and the ethacrynic acid-sensitive sodium efflux from erythrocytes of patients with cystic fibrosis are both decreased. Furthermore, the ouabain-sensitive adenosine triphosphatase activity is diminished in the red blood cell ghosts of these patients. Perhaps of greater significance is the fact that ethacrynic acid-sensitive sodium efflux is clearly diminished in the erythrocytes of the asymptomatic parents of these sick children. This defect in sodium transport may be valuable for detecting the heterozygous carrier state.

The activity of the ouabain-sensitive sodium-potassium-activated component of the ATP-hydrolyzing enzyme system (ouabain sensitive ATPase) was studied in the erythrocyte membranes of 10 patients with hyperthyroidism, and found to be decreased in all 10 patients. The mean ouabain-sensitive ATPase activity was 43 +/- 4 nmol Pi/mg tissue/h in the patients, compared with 69 +/- 5 nmol Pi/mg tissue/h in the erythrocyte membranes of 10 paired control subjects. The mean concentration of sodium within the erythrocytes was 10.8 +/- 0.9 nmol/liter of red blood cells in the patients and 7.2 +/- 0.3 nmol/liter of red blood cells in the controls. The decrease in ouabain-sensitive ATPase activity did not appear to be associated with a change in the ligand sensitivity of ATPase, nor was there a difference in the activity of the ouabain-insensitive component of ATPase. Serial studies to follow the effects of treatment of hyperthyroidism on red cell membrane ATPase were performed repeatedly in one of these patients. There was a significant inverse correlation between L-thyroxine (T4) and ouabain-sensitive ATPase, as both variables returned to normal. Normal erythrocyte membranes were assayed for ATPase activity in the presence of varying concentrations of L-triiodothyronine (T3) and T4, and following pre-incubation with T4. No significant effect on erythrocyte membrane ATPase was demonstrated in either series of experiments. It can be concluded from these studies that the decreased sodium efflux in the erythrocytes of patients with hyperthyroidism is associated with a decrease in the activity of the ouabain-sensitive component of ATPase in the erythrocyte membrane. The failure to reproduce this effect in vitro suggests that it does not represent a direct effect of the thyroid hormones on the mature erythrocyte membrane.