Rb+ influxes differentiate between growth arrest of cells by different agents
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The effect of cell cycle on Rb+ (K+) fluxes was studied in NIH 3T3 mouse fibroblasts. Serum starvation or isoleucine deprivation resulted in cell arrest at an earlyG1/G0 phase, accompanied by a marked decrease in both ouabainsensitive and ouabain-resistant Rb+ influx. On the other hand, cells arrested at lateG1/G0 phase by hydroxyurea treatment have high ouabain-sensitive and ouabain-resistant Rb+ influx. Butyric acid treatment resulted in cell arrest at an earlyG1/G0 phase, but in contrast to serum or isoleucine starvation did not decrease Rb+ influxes. It is thus shown that quiescent cells may have Rb+ influx rates as high as that of logarithmically growing cells. The results are consistent with the hypothesis that an increased ion permeability of the cell is initiated at a critical stage inG1/G0 phase, and that butyric acid may arrest the cell beyond that stage.
Key Wordsouabain-resistant ouabain-sensitive Rb+ influx
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