Jpn. J. Pharmacol. 72, 347-353 (1996)

Ouabain-Induced Cell Proliferation in Cultured Rat Astrocytes

Yosuke Murata, Toshio Matsuda, Kazuko Tamada, Rie Hosoi (#1), Shoichi Asano, Kazuhiro Takuma (#2), Koh-ichi Tanaka (#3) and Akemichi Baba (*)

Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565, Japan(#,1) Present address: Department of Medical Physics, Faculty ofMedicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565,Japan
(#2) Present address: Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Nishi-ku, Kobe 651-21, Japan
(#3) Present address: Department of Pharmacology, Kagoshima University Dental School, Kagoshima 890, Japan
(*) To whom correspondence should be addressed.

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 x 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 hemocytometer. 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 astrocytes, ouabain did not stimulate [3H]thymidine incorporation into C6 glioma and fibroblast cells. The effect of ouabain on [3H]thymidine incorporation in astrocytes 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 astrocytes in cell-specific and Ca2+-dependent manners.

Keywords: Ouabain, Na+,K+-ATPase, Cell proliferation, Thymidine incorporation, Astrocyte