Fig. 1

H₂O₂ induces PS externalization in HK1 and NP69 cells. HK1 cells were either left untreated or treated with 50 µM of H₂O₂ for 4 and 8 h, whereas NP69 cells were either left untreated or treated with 100 µM of H₂O₂ for 16 and 24 h. The cells were then subjected to flow cytometric analysis of PS externalization as described in “Methods” section. Cells treated with CPT were included as a positive control. Percentages of apoptotic cells expressing PS were determined in (a) (i) HK1 and (b) (i) NP69 upon H₂O₂ treatment. Means and SD from three independent experiments carried out in duplicate are shown. Student’s t test was used for statistical analysis to compare treated groups with untreated control, *p < 0.05. Representative dot plot diagrams showing the apoptotic populations of (a) (ii) H₂O₂-treated HK1 cells and (b) (ii) H₂O₂-treated NP69 cells detected by Annexin V-FITC and PI staining are shown. The lower left quadrants show viable cells; the lower right quadrants represent early apoptotic cells; the upper right quadrants show late apoptotic and necrotic cells