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Enzyme Activities Associated with Carcinogen Metabolism in Liver and Nonhepatic Tissues of Rats Maintained on High Fat and Food-Restricted Diets¹

Laboratory for Cellular and Biochemical Toxicology, Department of Pharmacology and Toxicology, Rutgers University, Piscataway, NJ 08854 ^* Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599

The influence of high fat or food-restricted diets on key enzymes associated with polycyclic aromatic hydrocarbon metabolism was assessed in liver, lung, kidney and stomach of rats. Animals had access ad libitum to the AIN-76A purified diet (control) or were given 65% of the intake of controls for 3 wk. The high fat diet was isoenergetic to the control diet by substituting corn oil for equal energy from carbohydrate and addition of cellulose to obtain equal energy density. Activities of arylhydrocarbon hydroxylase and 7-ethoxycoumarin O-deethylase were significantly increased in lungs of food-restricted rats and decreased by the high fat diet but were not altered in liver. Both diets increased arylhydrocarbon hydroxylase approximately twofold in kidney. Glucose 6-phosphate and 6-phosphogluconate dehydrogenase were lowered in lung, kidney and liver by the high fat diet. Hepatic glutathione S-transferase was increased by high fat feeding. Food restriction decreased activities of arylsulfatase and ß-glucuronidase about 40% in lung. Hepatic arylsulfatase was also decreased about 40% by this treatment. Changes in hydrolase activities in livers and lungs of animals maintained on restricted diets raises the interesting possibility that net production of glucuronide and sulfate conjugates of carcinogens by the liver and their hydrolysis in lung is altered by food restriction.

KEY WORDS: • food restriction • high fat diet • extrahepatic tissues • xenobiotic metabolizing enzymes • rats

¹ Supported, in part, by a grant from the National Cancer Institute (CA 20807)

Manuscript received 10 January 1990. Revision accepted 31 July 1990.