Inhibition of cell cycle in erythroid cells cocultivated with HZ or treated with HNE. Erythroid cells were cocultivated with HZ (25μM HZ-heme), treated with HNE (7μM), or kept as untreated controls (C) in liquid culture. For assessment of cell cycle, cells were stained with PI and analyzed for DNA content by flow cytometry. Percentage of cells in G₀/G₁ (A), S (B), and G₂/M (C) phase of cell cycle was determined. Means ± SE of 5 independent experiments. The significance of differences (*P < .05) between controls and HZ-treated or HNE-treated cells are indicated.