Murata Y, Matsuda T, Tamada K, Hosoi R, Asano S, Takuma K, Tanaka K, Baba A
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Japan.
Jpn J Pharmacol. 1996 Dec;72(4):347-53. doi: 10.1254/jjp.72.347.
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 Ca(2+)-dependent manners.
哇巴因不仅显著刺激星形胶质细胞掺入[3H]胸苷，还刺激其掺入[3H]尿苷。分别在加入哇巴因后的36 - 48小时和12 - 72小时观察到这些效应。胸苷掺入的剂量 - 反应曲线和尿苷掺入的剂量 - 反应曲线均为钟形，胸苷掺入的峰值出现在10^(-3) M，尿苷掺入的峰值出现在2×10^(-3) M。通过使用3 - (4,5 - 二甲基噻唑 - 2 - 基)-2,5 - 二苯基四氮唑溴盐的测定法以及使用血细胞计数器的方法确定，哇巴因增加了细胞数量。低浓度的细胞外K+模拟了哇巴因刺激[3H] - 胸苷掺入的作用，而高浓度的细胞外K+则阻断了哇巴因的作用。与星形胶质细胞不同，哇巴因不刺激C6胶质瘤细胞和成纤维细胞掺入[3H]胸苷。哇巴因对星形胶质细胞[3H]胸苷掺入的作用依赖于细胞外Ca2+，并且被放线菌酮阻断。这些发现表明，长时间抑制Na+，K(+)-ATP酶以细胞特异性和Ca(2+)依赖性方式导致培养的星形胶质细胞增殖。
