[The vehaviour of monoaminooxydase (MAO) activity in tumours. I. MAO activity measurement in experimental tumours (author's transl)].

The activity of MAO (EC 1.4.3.4) was measured in liver homogenates of mice with experimental tumours Sarcoma S-180 and Leukemia L-1210. The enzyme activity was determined by two methods: spectrophotometric--with benzylamine as a substrate and the second with the application of oxygen electrode and adrenaline as a substrate. An increase of the enzyme activity was observed in liver homogenates of mice with Sarcoma S-180 as compared with the controls. High activity of MAO with both substrates was also observed in Sarcoma ascites. In Leukemia L-1210 changes of activity in relation to adrenaline as a substrate were very small, but towards benzylamine the affinity of enzyme was higher (the increase of activity was about 50%).