[Effect of ionizing radiation and physical loads on pyrimidine-5'-nucleotidase activity in rat liver subcellular fractions].

Activity of pyridine-5'-nucleotidase in the mitochondria and postmitochondrial supernatant of the rat liver has been studied as affected by the radiation and physical load (running till tiredness). It is shown that physical load leads to double increase of cytidinemonophosphatase activity and does not actually affect uridine monophosphate one. Irradiation evokes changes of cytidine monophosphatase activity of the studied fractions in time: 1 year after irradiation it increases by 45%, 1 day later it sharply changes and 3 days later it increases again. Mutual action of the irradiation and physical loading 1 year after the irradiation causes the decrease of uridine monophosphatase and cytidine monophosphatase activity and 3 days later their amount increases, especially in the postmitochondrial supernatant (2-53 times). Thus the data obtained show that the effect of the radiation and physical loading evoke rather essential and stable changes in the activity of key enzymes of uridine monophosphate and cytidine monophosphate.