Lithium therapy and the turnover of phosphatidylcholine in human erythrocytes

In 17 lithium-treated patients with manic-depressive disorders and 11 healthy subjects the concentrations of choline, phosphorylcholine, cytidyldiphosphate choline, lipid bound choline, and glycerophosphorylcholine were measured in plasma and erythrocytes. Plasma levels of high density, low density, and very low density lipoproteins were also estimated as well as the concentrations of 4 free fatty acids. Free choline (more than 10-fold) and phosphorylcholine (2-fold) were significantly increased in erythrocytes of lithium-treated patients as compared to the healthy untreated controls. Differences in the other substrates were not significant. Osmotic resistance of the erythrocytes was not changed during lithium treatment. Inhibition of the choline flux across the erythrocyte membrane in vitro from lithium-treated patients was not abolished by equilibration of the concentration gradient. It is concluded that the accumulation of choline in erythrocytes from patients on lithium therapy may be due to trapping of lipid derived choline because of an alteration in membrane permeability and not to increased breakdown of phosphatidylcholine.