Oxidant-induced changes in the cellular energy homeostasis. A study with 3,5-dimethyl N-acetyl-p-benzoquinone imine and isolated hepatocytes.

Exposure of isolated hepatocytes to 400 microM 3,5-dimethyl N-acetyl-p-benzoquinone imine (3,5-diMe NAPQI), rapidly induced the formation of plasma membrane blebs. More than 50% of the viable cells were affected after 1 min incubation with 3,5-diMe NAPQI. Rapid loss of mitochondrial ATP, and sequential increases in ADP and AMP accompanied hepatocyte blebbing. 3,5-diMe NAPQI also induced a pronounced elevation of mitochondrial NADP level, whereas the NAD concentration was unaffected. Similar alterations in the adenine and pyridine nucleotide pools were found to occur in the cytosol, although at slower rates. During the initial phase of ATP loss and NADP production, there was also a concomitant decrease in the oxygen uptake of the hepatocytes. The decreases in energy substrates occurred in parallel to an increased uptake of trypan blue into the cells. Treatment of the hepatocytes with dithiothreitol, following 4 min exposure of the cells to 3,5-diMe NAPQI, reversed the quinone imine-induced changes in nucleotide levels and reduced the cytotoxicity. It is concluded that alteration of mitochondrial function, which results in changes in the cellular energy homeostasis, is an important event in the development of cytotoxicity caused by 3,5-diMe NAPQI.