Transitions of hepatic purine metabolism of Ehrlich ascites tumor bearing mice in different phases of tumor growth.

The concentrations of purine nucleotides, nucleosides and nucleobases in hepatocytes taken from healthy control mice and from Ehrlich ascites tumor bearing mice have been measured. The level of adenine nucleotides in the hepatocytes was higher during the proliferating phase in comparison with the resting phase of tumor growth and with control mice hepatocytes. The tracerkinetic studies on purine catabolism have been carried out on liver cells at different periods of tumor growth. The dynamics of radioactive tracers was mathematically modelled by a system of differential equations for both the concentrations and the specific radioactivities of the metabolites. Large differences in metabolic flux rates between control hepatocytes and hepatocytes in different phases of tumor growth were observed. The final purine degradation of hepatocytes was found to be accelerated in the resting phase but not in the proliferating phase of tumor growth. This result is in accordance with increased ATP concentration of liver itself in the proliferating phase of tumor growth. A conclusion is possible that the liver does not supply nucleosides and nucleobases for the Ehrlich ascites tumor cells during the proliferating phase of tumor growth.