Transmembrane distribution of lithium and sodium in erythrocytes of depressed patients

In this investigation the intracellular: extracellular distribution of lithium across the erythrocyte membrane (RBC lithium distribution) was studied in vitro and in vivo. The in vitro studies were conducted by incubating cells from drug-free subjects in lithium-containing physiologic media. The in vivo studies consisted of measurements of plasma and erythrocyte (RBC) lithium and sodium concentrations during lithium carbonate treatment. Previous observations of a correlation between in vitro and in vivo RBC lithium distribution values were verified, and it was found that addition of 0.1 mM ouabain to the in vitro incubation media abolished this correlation. To examine the relationship between RBC lithium distribution and specific clinical features of depression, in vitro studies were conducted with RBCs from 20 depressed patients and 14 nondepressed control subjects. The patients were categorized as having bipolar (manic-depressive), unipolar, or secondary depressive disorders. After in vitro incubation with lithium for 48 h, the RBCs from bipolar patients had lithium distribution values that were similar to those observed in ouabain-treated cells. It appears that the lithium transport characteristics of RBCs of bipolar patients may differ from those of other depressed patients or nondepressed subjects.