Ouabain-Induced Cell Proliferation in Cultured Rat Astrocytes

Abstract

Ouabain markedly stimulated not only [³H]thymidine incorporation but also [³H]uridine incorporation into astrocytes. The effects were observed at 36-48 hr and 12-72 hr after addition of ouabain, respectively. The dose-response curves were both bell-shaped types with a peak at 10⁻³ M for thymidine incorporation and 2 × 10⁻³ M for uridine incorporation. Ouabain increased cell number as determined by an assay using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide and by a method using a hemocyiometer. Low concentration of external K⁺ mimicked the effect of ouabain in stimulating [³H]-thymidine incorporation, and high concentration of external K⁺ blocked the effect of ouabain. In contrast to astrocyies, ouabain did not stimulate [³H]thymidine incorporation into C6 glioma and fibroblast cells. The effect of ouabain on [³H]thymidine incorporation in astrocyies was dependent on external Ca²⁺, and it was blocked by cycloheximide. These findings indicate that prolonged Na⁺, K⁺-ATPase inhibition causes cell proliferation in cultured astrocyies in cell-specific and Ca²⁺-dependent manners.