The enzyme(s) threonine dehydrase (TDH) and serine dehydrase (SDH) were assayed in several hepatomas to determine the level in chow-fed, nonadrenalectomized and adrenalectomized hosts and high protein-fed, nonadrenalectomized and adrenalectomized animals. The capacity of the hepatomas to respond to the high protein stimulus varied from tumor to tumor and also, with one tumor, was dependent on the presence of adrenocorticosteroids. The effect of portal vein ligation on the capacity of hepatic tissue to respond with increased TDH and SDH to a high protein diet was studied, and the results were related to the dietary effects seen in hepatomas. The variable enzyme patterns are discussed in relation to the possibility that there may be “multiple pathways” by which a normal cell may become malignant.

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This work was supported in part by a grant (C-646) from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service.

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