DISTRIBUTION OF ALCOHOL-DEHYDROGENASE AND THE LOW KM FORM OF ALDEHYDE DEHYDROGENASE IN ISOLATED PERIVENOUS AND PERIPORTAL HEPATOCYTES IN RATS

Hepatic damage induced by chronic alcohol abuse starts in the perivenous (PV) zone of the hepatic lobule. To explain this vulnerability in the PV zone, periportal (PP) and PV hepatocytes were isolated by digitonin-collagenase perfusion and the distributions of class I alcohol dehydrogenase (ADH) and the low-K(m) mitochondrial aldehyde dehydrogenase (ALDH) were studied. ADH was measured by three approaches i.e., specific activity, immunoreactive enzyme content and ADH mRNA level. ALDH was determined by specific activity and immunoreactive enzyme content. When compared with PV hepatocytes, isolated PP cells exhibited higher lactate dehydrogenase (PP/PV = 1.3-1.5), higher alanine aminotransferase (PP/PV = 1.7-1.9), but lower glutamine synthase (PP/PV < 0.01). By prelabeling the PP zone with acridine orange before digitonin-collagenase digestion, flow cytometry indicated that mainly the isolated PP hepatocytes exhibited fluorescence. ADH activities and ADH mRNA levels did not differ in PP and PV cells. With a polyclonal antibody directed specifically against class I ADH, ADH immunoreactive protein also did not differ in PP vs PV cells. By activity assay, the low K(m) ALDH activities were found to be lower in the PV hepatocytes (PP/PV = 1.3). This was confirmed by immunotransblot with anti-ALDH IgG (PP/PV = 1.6). In conclusion: the preferential damage of the PV zone produced by ethanol is not caused by differences of ADH distribution in liver but could be related partly to a decrease in the low-K(m) ALDH in the PV zone.