IH-induced cell death was associated with oxidative stress and PARP activation. A: Severe apoptosis appeared in the IH3day and IH4day groups. The administration of inhibitors significantly decreased the occurrence of apoptosis. B: There were more TUNEL (+) cells in the IH3day and IH4day groups. Addition of Phe resulted in a decrease in the ratio of TUNEL (+) cells. C: There were more PI (+) cells in the IH3day and IH4day groups. The ratio of PI (+) cells decreased significantly after the administration of inhibitors. *p < 0.05 for comparing each group with IH3day group or with IH4day group by Dunnett's test in ANOVA.