Metabolic adaptations in rat hepatomas. IV. Regulation of threonine and serine dehydrase

1963 Cancer Research  
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 adrenal ectomized 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
more » ... acity 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 â€oemultiplepathways― by which a normal cell may become malignant. The induction of hepatomas having enzyme profiles closely resembling normal liver (4, 6, 18) has provided a useful tool for the study of some mechanisms controlling the levels of specific en zymes involved in amino acid metabolism (9, 10, 12), in both normal and neoplastic tissue. In the first paper in this series (12) data on the effect of dietary protein content on tryptophan pyrrolase (TPO), threonine dehydrase (TDH), and dehydrase (SDH) in tumor and host liver of Morris 5128 hepatomas were presented. The first paper (12) also showed that Hepatoma 5128 grow ing in adrenalectomized animals had much lower levels of serine and threonine dehydrase than did tumors in nonadrenalectomized animals. The find ing that these enzymes in the 5123 were affected by dietary and hormonal influences (12) opened the door to the study of the control of enzyme levels in other â€oeminimal-deviation hepatomas― (10) in which comparisons with normal liver seemed justifiable. From these studies it might
pmid:14014306 fatcat:y4iter5wzjan5hizhtdaspxrgi