Regulation of Na+/K+-ATPase in bipolar disorder and lithium therapy has been investigated for more than 40 years. Contradictory results in this area may be caused by the difference between acute and long-term Li effects on cell metabolism and variance in responsiveness of different cell types. We compared the time-course of Li action focusing on Na+/K+-ATPase and lipid peroxidation in two widely different cell models-Jurkat and HEK293. Na+/K+-ATPase expression level was determined in cells cultivated in the absence or presence of 1 mM Li for different time spans (1, 7, and 28 days) using [3H] ouabain binding and immunoblot assay of α-subunit. In parallel samples, the formation of malondialdehyde (MDA) was quantified by HPLC, and 4-hydroxy-2-nonenal (4-HNE) protein adducts were determined by immunoblot. Cultivation of Jurkat cells in 1 mM Li medium resulted in downregulation of Na+/K+-ATPase (decrease of [3H] ouabain-biding sites and intensity of immunoblot signals) in all Li-groups. In HEK293 cells, the decrease of Na+/K+-ATPase was observed after the acute, 1-day exposure only. The long-term treatment with Li resulted in Na+/K+-ATPase upregulation. MDA and 4-HNE modified proteins were decreased in Jurkat cells in all Li-groups. On the other hand, in HEK293 cells, MDA concentration was decreased after the acute, 1-day Li exposure only; the long-term cultivations, for 7 or 28 days, resulted in a significant increase of lipid peroxidation products. The Li-induced decrease of lipid peroxidation products was associated with the decrease of Na+/K+-ATPase level and vice versa.

Department of Biomathematics Institute of Physiology of the Czech Academy of Sciences v v i Videnska 1083 14220 Prague 4 Czech Republic

Department of Psychiatry Dalhousie University Halifax Nova Scotia Canada National Institute of Mental Health Klecany Czech Republic

Department of Trace Element Analysis Institute of Analytical Chemistry of the Czech Academy of Sciences Brno Czech Republic