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Deviation in Esterase Isozyme Pattern during Early Stage of Hepatocarcinogenesis by 3'-Methyl-4-dimethylaminoazobenzene¹

Department of Pathology, Sapporo Medical College, Sapporo, Hokkaido 060, Japan

With 2-naphthyl acetate as a substrate, the activity and isoenzymic pattern of the nonspecific esterase were examined in the liver of rats fed 3'-methyl-4-dimethylaminoazobenzene.

In spite of the occurrence of hepatocyte degeneration in the early stage of hepatocarcinogenesis, the esterase activity did not decrease as did glucose 6-phosphatase activity. From the fact that the cell types constituting hepatic tissue revealed different isozyme patterns, changes in the esterase isozyme pattern and the activity of each individual esterase isozyme (without any remarkable change in the total activity of the hepatic tissue), seemed to reflect the degree of cell injury and alteration of cell population in the liver due to azo dye feeding.

The esterase isozyme pattern of hepatocytes, regenerated in the precancerous stage, was different from that of the original normal hepatocytes in the activity of the isozyme which demonstrated the greatest anodic mobility by cellulose acetate electrophoresis. Similar to the pattern of a developing liver, these regenerated hepatocytes were characterized by an immature type of esterase. This esterase pattern was observed in regenerating livers and in the noncancerous areas of tumor-bearing livers. The hepatoma pattern deviated more from the adult liver type than did precancerous liver and revealed a fetal type of esterase situated at the most cathodic side of the electrophoretogram. This fetal esterase is considered a cholinesterase, and the cholinesterase activity in hepatoma is much higher than in fetal and adult livers.

¹ This work was supported in part by Grants-in-Aid for Cancer Research (90287 and 90288) from the Ministry of Education, Japan.

Received 11/27/73. Accepted 3/26/74.