Erythrocyte membrane cation carrier, relapse rate of manic-depressive illness and response to lithium.

Biochemical studies of manic-depressive psychosis usually correlate biochemical findings with current affective state and hence any significant findings could be secondary to mood change. The present study attempts to correlate measures of the erythrocyte membrane cation carrier with clinical events, remote in time from the biochemical assay. Erythrocyte sodium concentration, ouabain-sensitive potassium influx and Na-K ATPase were estimated in 11 patients before and after the cross-over point in a 2-year double blind clinical trial of lithium. Patients with the lowest erythrocyte Na-K ATPase and the highest flux sodium ATPase ratio tended to suffer most episodes of affective illness in the 2 years. Patients who had a low initial Na-K ATPase or a high initial flux sodium ATPase ratio, or in whom this ratio fell most with lithium or whose Na-K ATPase rose most with lithium, clinically responded best to lithium.