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Irreversible Fixation of Increased Level of Muscle Type Aldolase¹ Activity Appearing in Rat Liver in the Early Stage of Hepatocarcinogenesis^,2

Cancer Research Institute, Faculty of Medicine, Kyushu University, Fukuoka, Japan

With the use of antimuscle aldolase sera, muscle type aldolase activity in the liver of adult rats was determined during a 60-day interval after stopping the administration of a diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene for 60 days.

The muscle type aldolase in the livers of rats thus treated was found to be elevated when compared to normal liver, although no appreciable differences were observed in total aldolase activity, mitotic index, histological architecture, and soluble protein, as well as DNA content.

The appearance of this enzymic change was already observable by administrating the azo dye only for 15 days.

The increased level of muscle type aldolase activity observed in the liver of rats fed azo dye for 60 days was maintained during a 300-day observation period.

A similar enzymic alteration could be induced by another hepatocarcinogen, N,N'-2,7-fluorenylenebisacetamide, whereas a noncarcinogen, 2-methyl-4-dimethylaminoazobenzene, failed to induce this change.

¹ In this paper we tentatively defined the liver enzyme neutralizable with antimuscle aldolase sera as "muscle type aldolase," distinguished from muscle aldolase, since the identity of both enzymes is not yet conclusively determined.

² This work was supported by a grant-in-aid for scientific research from the Ministry of Education, Japan.

³ Present address: Department of Orthopaedy, Faculty of Medicine, Kyushu University, Fukuoku, Japan.

Received 5/19/69. Accepted 8/19/69.