Lithium regulation of protein phosphorylation in rat cerebral cortex slices in vitro.

The aim of the present study was to evaluate the direct effect of Li+ and Na+-Li+ exchange on protein phosphorylation in rat cerebral cortex slices incubated in Krebs Ringer medium. When Na+ concentration was varied in the incubation medium, either by replacement with Li+ or sucrose, a variable effect on [32P] phosphate incorporation into proteins was observed. Protein phosphorylation in cerebral cortex slices was very low in the absence of Na+, and some dependence of phosphorylating system of neural tissue on extra cellular concentration of Na+ was evident. Lithium was not able to replace sodium as far as protein phosphorylation in cortical slices is concerned. Ouabain was more effective in a Li+ containing medium in inhibiting protein phosphorylation, presumably due to improper functioning of the sodium pump.