Changes in the free amino acids have been studied in the liver of fasted and force-fed tumorous and nontumorous rats with and without the injection of dl-ethionine.

In the presence of the tumor the level of aspartic acid, lysine, and serine increased in the fasted, untreated animals. The injection of ethionine caused an increase (methionine, lysine, and glutamic acid), no change (serine and proline), or a decrease (aspartic acid and glycine) of amino acids in the liver of nontumorous animals. In tumorous rats the injection of ethionine caused an increase of some amino acids (methionine, lysine, glutamic acid, serine, and proline) and a decrease of others (aspartic acid and glycine) in the liver. The changes in amino acids were greater in tumorous than in nontumorous animals.

It was concluded that the normal equilibrium levels of some amino acids of the liver were altered in animals bearing tumors. This conclusion was supported by the results from the force-feeding experiments.

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Paper No. 103. For the preceding related paper (No. 101) see Levy et al (6). This work was supported by grants from the American Cancer Society, the U.S. Public Health Service, and the Cancer Research Funds of the University of California. The authors are indebted to Mrs. Raymond C. Davis and Miss Sally Lovett for technical assistance.

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