(Top) Effect of hypoxia for different time intervals (10, 20, and 30 minutes) and reoxygenation (30 minutes) on free radical generation. (Bottom) Effect of variable time of reoxygenation (10, 20, and 30 minutes) on hypoxic cells. Cells were subjected to hypoxia for 15 (solid bars) or 30 (empty bars) minutes. Free radical generation response was induced by AA (1 to 5 × 10⁻⁵ mol/L) after H-R. *P < .01 in comparison with the control.