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Lithium (1-8 mM) caused a dose-dependent increase in the number of [3H]ouabain binding sites and in sodium/potassium (Na/K) pump activity in normal lymphocytes after incubation for 72 h. The increase in Na/K pump activity was due to an increase in the Vmax of the pump, with no change in the apparent affinity (Km) for potassium (rubidium). There was no change in the turnover number of the pump and the intracellular sodium concentration fell. The increase in [3H]ouabain binding sites was prevented by the addition of myo-inositol (10 mM), by inhibition of the protein kinase C with staurosporine (100 nM) and by inhibition of the Na/H antiport with dimethylamiloride (50 microM). These results suggest that the increase in Na/K pump activity caused by lithium is due to an increase in pump numbers and not due to increased activity of individual pumps or to an alteration in the affinity of the pumps for potassium. The increase in Na/K pump numbers and activity in lymphocytes exposed to lithium for 72 h may be related to altered Na/H antiport activity secondary to inhibition of phosphoinositol breakdown by lithium.

Type

Journal article

Journal

Biochim Biophys Acta

Publication Date

17/04/1991

Volume

1092

Pages

138 - 144

Keywords

Adult, Alkaloids, Amiloride, Carrier Proteins, Female, Humans, Inositol, Lithium, Lymphocytes, Male, Ouabain, Potassium, Protein Kinase C, Rubidium, Sodium-Hydrogen Antiporter, Sodium-Potassium-Exchanging ATPase, Staurosporine