[Polyamine oxidative deamination in hepatomas with varying growth rates]

Rates of oxidative deamination of polyamines were studied in rapidly growing hepatomas G-22 and G-27, in slowly growing hepatomas G-60, G-61, G-48, G-46 as well as in liver tissue of tumor-bearing animals and animals treated with nitrose piperidine. Diamine oxidase activity was not found in rapidly growing hepatomas. Treatment with pyridoxal-phosphate did not restore the diamine oxidase activity in hepatomas G-27, but distinctly increased the latter in the liver tissue of the tumor-bearing animals up to the level of the enzymatic activity found in liver tissue of the intact animals. On the contrary, high concentrations of pyridoxal-phosphate (above 0.02 mg) inhibited the diamine oxidase activity in liver tissue of the impaired and intact animals. The enzymatic activity was markedly decreased in slowly growing hepatomas G-60, G-61, G-48 and G-46 as compared with the activity in liver tissue of tumor-bearing animals. Oxidation of all the substrates used could be measured using hepatoma G-60, putrescine and spermidine - for hepatoma G-61, but only putrescine - for hepatoma G-48. No of the substrates used was deaminated by hepatoma G-46. Four-fold decrease in the diamine oxidase activity was observed during malignization of liver cells induced by nitrose piperidine. The diamine oxidase was mainly localized in the postmitochondrial fraction of hepatocytes.