Plasma and erythrocyte choline concentrations in rats following chronic treatment with lithium or choline

Rats were given daily injections of choline, lithium or lithium plus choline for either 11 or 18 days and red cell choline, glycine and glutathione levels were measured using proton nuclear magnetic resonance spectroscopy. In addition, plasma choline, plasma lithium and red cell lithium levels were measured 4 hr after the last dosage. Choline (1 mmol/kg) alone increased plasma but not red cell choline concentrations. Lithium (0.94 mmol/kg) elevated red cell choline levels but did not affect plasma choline concentrations. In contrast, red cell choline levels were not elevated in rats treated with a higher dose of lithium (1.88 mmol/kg). When choline was given in addition to the lower dose of lithium, a similar accumulation of red cell choline was observed suggesting that the lithium-induced choline accumulation was not enhanced by a greater availability of free choline. No differences were detected in red cell glycine or glutathione levels between any of the treatment groups. Therefore, lithium produced a specific (dose-dependent) accumulation of choline in rat erythrocytes. However, the 100% increase observed in rats was not as marked as the increased red cell choline levels reported in patients maintained on lithium (8 to 10-fold). This discrepancy supports the concept that species differences exist in red cell choline transport or metabolism.