Figure 1.

Cell survival depends on the dose of ouabain. (a) U937 cells were exposed or not to different concentrations of OUA for 24 h. Cells were counted in a hemocytometer as excluding and not excluding trypan blue. Viability was obtained by calculating live cells (trypan blue-excluding) as percentage of all counted cells. A portion of cells were fixed and stained with propidium iodide; subG1 events in the cell cycle were evaluated under cytofluorimetry. The reported values represent the means and the error bars the S.D. of the percentage of live cells (trypan blue-excluding) or subG1 events of six independent experiments. Assessment of cell survival was investigated and statistically significant differences (P<0.05) were found between the data obtained using ouabain 100 nM and the two highest concentrations of the drug. (b) illustrates the percentage of events in the cell cycle phases of cells untreated or treated with ouabain 100 nM for 24 h. Values are means±S.D. of six experiments.