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The Metabolism of Aromatic Amino Acids in Leukemic Rats^*

Victor H. Auerbach and Harry A. Waisman

( Sarah A. Workman Pediatric Research Laboratory, Dept. of Pediatrics, Medical School, University of Wisconsin, Madison, Wis.)

1. Plasma tryptophan, tyrosine, and phenylalanine levels were found to be elevated in rats bearing the J strain of leukemia.

2. The corresponding liver enzymes tryptophan peroxidase-oxidase, tyrosine transaminase, phenylalanine transaminase, and phenylalanine hydroxylase, were studied in these animals under a variety of conditions.

3. The elevated plasma tryptophan and tyrosine levels are not due to a decrease in the catabolic potential of the liver. On the contrary, the high plasma amino acid levels are maintained in spite of the increased enzyme levels which may be a result of substrate-induced adaptations.

4. The high phenylalanine plasma level is in part due to the absence of phenylalanine hydroxylase in the livers of J leukemic animals. The phenylalanine hydroxylase activity of healthy rats was found to be depressed by the administration of tyrosine. The interactions between the various amino acids and the corresponding enzyme systems are discussed.

5. The degree of infiltration of the livers of J leukemic rats by leukocytes has been estimated by enzymatic means as 35 per cent of the total mass.

^* This investigation was supported in part by research grant CY-3258 from the National Institute of Health and by an institutional grant from the American Cancer Society.

Present address: Dept. of Pediatrics, Temple University, Philadelphia, Pa.

Received 11/14/57.

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