Transaminase activities of liver tumors and serum
The glutamic oxalacetic transaminase (GOT) activities of five transplanted malignant liver tumors were compared, as well as that of mammary adenocarcinoma 6338, the Walker carcinosarcoma ~56, and the livers and sera of the host rats. Bile and urine were analyzed in some additional experiments with Hepatoma 51~3. The GOT activity of Hepatoma 51~3, unlike that of the Dunning, the Novikoff, the Morris 3683, and the Sidransky ethionine-induced hepatomas, was greater than that of liver. The livers
... liver. The livers of the host animals had approximately the same transaminase activities as livers of tumor-free animals of the same ages. No strain or sex differences were observed. An elevation in serum GOT was observed in rats bearing the transplanted tumors. The amount of elevation was sometimes insignificant with the Novikoff tumor and was moderate with the other tumors studied, except with Hepatoma 51~8, which was associated with an elevation of 300-4000 per cent of normal. The degree of elevation was dependent upon the specific tumor type, but within the range of increase for the type, serum GOT activity increased proportionally with the weight of the transplant with 51~3, and also with the Novikoff and the Sidransky liver tumors. Tumorectomy of 51~3 was followed by a decrease to a normal level of serum GOT in 48 hours. Urine and bile contained very little GOT activity compared with that of serum. GOT activity was increased in these two excretory fluids with increased serum GOT, but the amount of increascd activity found accounted for little of the activity that disappeared from the blood following tumorectomy of 51~3, or following the intraperitoneal injection of a GOT-rich tumor extract. The high GOT activity in the slowly growing Hepatoma 51~3, and the very low activity in the Novikoff, the fastest growing of the tumors examined, is in accord with an earlier observation of Cohen et al. that there is an inverse relation of GOT activity to rate of growth of tissues, including liver. Kit and Awapara (10), in a report on the transaminase activity of lymphatic tissue and lymphosarcoma, marked the widespread distribution of transaminases in animals, plants, and microorganisms. Transaminases are concerned with the transfer of the amino group from certain amino acids to keto acids to produce other amino acids. One might therefore have expected a priori that fast growing tissues would contain high concentrations of these enzyme activities which can help furnish amino acids required for protein synthesis. Proof, however, of a possible role of transaminases in peptide and protein synthesis is lacking (14) . Received for publication ffune 12, 1961. Furthermore, Braunstein (3) observed that glutamate-aspartate and glutamate-alanine transaminase activities of tumors were about the same or lower than that of the normal tissues which were used for comparison. Cohen, Hekhuis, and Sober (4) concluded that rapidly growing tissues had a low transaminase content after finding that different mouse tumors, fetal cat tissues, and regenerating rat liver showed a decreased transaminase activity, when the fetal tissues were compared with corresponding adult tissues, and regencrating liver with normal liver. Since the mouse tumors could not be satisfactorily compared with related normal tissues, they studied glutamic- 15~ Research. on July 10, 2020.