CHANGES IN THE ADENYLIC ACID DEAMINASE ACTIVITY OF RAT LIVER DURING CARCINOGENESIS.

Abstract

Summary Changes in the adenylic acid (AMP) deaminase activity of rat liver during azo dye hepatocarcinogenesis were studied to determine whether they were related to malignant transformation. The AMP deaminase activity of rats fed 3′-methyl-4-dimethyl-aminoazobenzene (3′-Me-DAB) for 4 weeks was increased 1.5- to twofold compared with that of control animals fed basal diets. The elevated activity persisted throughout 12 weeks. If 3′-Me-DAB was withdrawn from diets after 4, 8, or 12 weeks, AMP deaminase activity returned to control levels within 7–10 days. No appreciable increases in enzyme activity were observed during regeneration following partial hepatectomy. Animals fed 4′-fluoro-DAB showed increases in hepatic AMP deaminase activity; however, animals fed 4′-Me-DAB or o -aminoazotoluene failed to show increases throughout 12 weeks. Hypophysectomized rats fed 3′-Me-DAB for 6 weeks showed no increases in AMP deaminase activity. Similarly, the simultaneous feeding of p -hydroxypropiophenone and 3′-Me-DAB greatly delayed the usual increases in in AMP deaminase activity. Feeding α-naphthyl isothiocyanate caused early increases in deaminase activity; however, activity subsequently returned to the normal range. Animals that were fasted and then fed a low protein diet also showed elevated AMP deaminase activity. It was concluded that the elevation of AMP deaminase activity in precancerous rat liver ( a ) was related to azo dye carcinogenesis, ( b ) was not associated intrinsically with regeneration or with biliary proliferation, and ( c ) was not a phenomenon exclusively characteristic of precancerous liver.