Erythrocyte cation transport disturbances in patients with endogenous depression

The active cation transport mechanisms (ouabain-dependent fluxes of sodium; ODS) and potassium (ODK), sodium-potassium adenosine triphosphatase ([Na+-K+]-ATPase) activity as well as lithium-sodium countertransport (LSC) reflecting sodium exchange diffusion, were studied in erythrocytes of forty-four patients with endogenous depression both in acute episode and in remission, and compared with thirty healthy control subjects. During depressive episodes, the activities of all mechanisms studied were significantly lower than those of control subjects. In female depressives the values of ODS and LSC were lower than in males. In remission, the activity of all mechanisms rose, reaching in most patients the values of control subjects. In female patients, activities of ODS and LSC were still lower than in male patients and female controls. The activities of ODS and LSC had the highest discriminating power between depressive patients and control subjects. It appears that membrane pathology may be an aetiologic factor in endogenous depression. A disturbance in erythrocyte transport presents most conspicuously during depressive episodes and in some patients may also persist to the normothymic period.