Effect of Hypokalaemia on the Ouabain-Sensitive Sodium Transport and the Ouabain-Binding Capacity in Human Erythrocytes

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Abstract
The Na content, the ouabain-sensitive Na efflux and efflux rate constant and the ouabain-binding capacity were measured in the erythrocytes of 53 patients with hypokalemia and in 37 healthy controls. The Na content alone was measured in a further 57 patients with hypokalemia. In the patients with hypokalemia there was an increase in the average Na content of the erythrocytes, which was entirely due to a reduction in the ouabain-sensitive efflux rate constant. The ratio of the ouabain-sensitive efflux rate constant to the number of Na pumps was decreased in the patients with hypokalemia, and was directly related to the plasma K. Many patients with moderate hypokalemia had normal erythrocyte-Na and K contents and normal ouabain-sensitive efflux rate constant. These patients had an increased number of Na pumps, which compensated for the inhibitory effect of hypokalemia on each Na pump. This increase in the number of Na pumps was common even in patients who had probably had hypokalemia for less than 2 wk. There apparently are latent Na pumps within the circulating erythrocytes.