Role of ethanol‐inducible cytochrome P‐450 IIE1 in carbon tetrachloride—induced damage to centrilobular hepatocytes from ethanol‐treated rats

The ethanol-inducible form of cytochrome P-450 (IIE1) is expressed and induced by ethanol, predominantly in the centrilobular region. Because this isoenzyme has a particularly high capacity to convert carbon tetrachloride and several other hepatotoxins into reactive intermediates, its role in producing damage was studied by comparing the effect of carbon tetrachloride exposure on hepatocytes isolated from either the periportal or the perivenous region by digitonin-collagenase perfusion. After exposure for 18 hr of primary culture to 600 μmol/L of carbon tetrachloride, periportal cells were only slightly damaged, as estimated from dye exclusion and lactate dehydrogenase leakage. In marked contrast, perivenous cells, which contained a several-fold higher amount of immunoreactive P-450 IIE1 apoprotein, were partly damaged after exposure to 60 to 150 μmol/L of carbon tetrachloride and severely damaged after 600 μmol/L. Similarly, lipid peroxidation after carbon tetrachloride was much more prominent in perivenous cells. The differences between perivenous and periportal cells in carbon tetrachloride—induced injury were larger when cells were isolated from chronically ethanol-treated rats. Isoniazid, an efficient inhibitor of P-450 IIE1, protected against damage by carbon tetrachloride more efficiently than the general P-450 inhibitor cimetidine. Our results suggest that the greater susceptibility of the perivenous hepatocytes to carbon tetrachloride—induced damage is associated with the high expression of P-450 IIE1 in these cells. This enzyme may also be involved in damage elicited by several other typical centrilobular hepatotoxins. (HEPATOLOGY 1990;12:1092–1097).