Pro-oxidative toxicity of cells in suspension does not point to a cell cultural artefact as an explanation of the increased susceptibility of alveolar epithelial-like cells after glucocorticoid pretreatment

•Pro-oxidative toxicity did not seem to be cell number dependent.•Increased toxicity of hydrogen peroxide in suspensions compared to monolayers.•Decreased toxicity of zinc chloride in suspensions compared to monolayers.•Zinc and tBHP pro-oxidative toxicity does not seems to be glutathione-dependent.•Hydrogen peroxide-derived toxicity seems to be glutathione-dependent. The influence of cell numbers on peroxide-(tertiary butylhydroperoxide (tBHP) or hydrogen peroxide-(HP)) or zinc-(zinc chloride) induced oxidative stress was assessed in alveolar epithelial-like cell lines in this work. Differences in cell numbers change the cellular glutathione and glutathione reductase activity as well as the amount of exported glutathione and therefore might influence susceptibility against oxidative stress. Toxicity due to zinc decreased, toxicity due to HP increased, while tBHP-mediated toxicity was unchanged in our experiments when cells were exposed in suspension as compared to monolayers. Toxicity of HP correlated to the glutathione content in monolayers and in cell suspensions, while zinc- or tBHP-mediated toxicity did not correlate towards glutathione. Decreasing cellular glutathione and the activity of some antioxidative enzymes by glucocorticoid pretreatment had no effect on toxicity of zinc or tBHP in L2 cells in suspensions, while toxicity in monolayers was increased. Glucocorticoid pretreatment seems to increase toxicity of HP in A549 monolayers according to the lowered protein content, while toxicity might be changed by a different way when cells are incubated as cell suspensions. No explanation as a cell culture artificial effect was observed, therefore we assume the increased toxicity after glucocorticoid pretreatment occurs in vivo as well.