INTRALOBULAR AND INTRACELLULAR-LOCALIZATION OF ALCOHOL-DEHYDROGENASE (ADH) ISOZYMES IN MOUSE-LIVER - BASIC ADH (CLASS-I) AND ACIDIC ADH (CLASS-III)

Localization of alcohol dehydrogenase isozymes [basic alcohol dehydrogenase (ADH): Class I and acidic ADH: Class III] was studied at both lobular and cellular levels in mouse liver by using immunohistological methods. The immunofluorescent microscopy showed that the basic ADH is distributed more predominantly in the perivenous zone than in the periportal zone, although the enzyme was detected in every parenchymal cell within the whole hepatic lobule. By immunoelectron microscopy, the enzyme was shown to distribute within the cytoplasmic matrix of hepatocytes, except for glycogen areas. On the other hand, acidic ADH was found to localize mainly on the periphery of the parenchymal cell, showing no distinct localization within the liver lobule by the immunofluorescent microscopy. The immunoelectron microscopic study confirmed that the acidic ADH localizes in the sinusoidal endothelial cells of the liver and revealed that the enzyme is also distributed in phagocytotic vesicles within hepatocytes. Thus, the basic and acidic ADH isozymes localize differently from each other in mouse liver tissue including parenchymal and nonparenchymal cells. These findings suggest that ADH isozymes may play different roles from each other in alcohol metabolism in the liver, not only at the enzymic property level but also at the cellular level.