The effect of lymphoma and other neoplasms on hepatic and plasma enzymes of the host rat.

Considerable thymidine kinase and pyrroline-5-carboxylate reductase activities were found in the plasma of rats bearing a transplanted lymphoma; neither activity was detected in plasma of hosts carrying hepatic, renal, mammary, or submaxillary gland tumors. All host livers exhibited signs of biochemical immaturity as indicated by the appropriate increases or decreases in the concentrations of the nine enzymes measured. The extent and time schedule of the changes in host liver varied with the enzyme and with the tumor that caused them. The hepatic concentrations of ornithine aminotransferase, arginase, pyrroline-5-carboxylate reductase, and glucokinase (all diminished), and of peptidyl proline hydroxylase and hexokinase (increased) were sensitive indicators of tumor growth in general. The concentration of ornithine aminotransferase decreased before the tumors became palpable. At more advanced stages, the high hepatic thymidine kinase activity distinguished the presence of hepatoma and lymphoma from those of all other equally fast-growing tumors. However, only in lymphoma-bearing rats did a fivefold elevation of hepatic thymidine kinase occur as early as 4 days after implantation. Additional observations on the lymphoma itself, on blood cells, and on the involuting thymus of normal rats indicate that the striking systemic effects of this tumor cannot be explained by a release of enzymes from the thymus or by the increased number of lymphoma cells present in blood or liver.