Propyl gallate-induced DNA fragmentation in isolated rat hepatocytes

Incubation of isolated rat hepatocytes with propyl gallate (PG) at concentrations of > or = 1 mM induced cell killing, whereas PG at < or = 0.5 mM did not cause cell death during a 3-h incubation. PG at > or = 0.5 mM elicited the ladder formation of soluble low-molecular weight DNA fragments with integer multiples of approximately 180 bp and specific nuclear DNA cleavages detected cytopathologically by labeling of a digoxigenin-nucleotide complex to new 3'-OH ends. Both of these PG-induced changes observed in hepatocytes are characteristic features of apoptosis. In contrast, the pretreatment of N-acetylcysteine (4 mM), a precursor of intracellular glutathione (GSH) and antioxidant, prevented PG (0.5 mM)-induced formation of soluble DNA fragments and loss of cellular GSH, ATP, and formation of blebbing. These results suggest that when the concentration of PG is decreased, the effects of PG on hepatocytes change from acute necrotic to apoptotic mode, and that the onset of DNA fragmentation is associated with GSH depletion.