[Post-irradiation changes in blood 5'-nucleotidase activity of rats after chronic exposure to gamma irradiation].

Kinetics of 5'-AMP hydrolysis by rat's blood serum was studied at 3, 10, 30, 90 and 180 days after prolonged gamma-irradiation at 0.1-1 Gy doses (60Co source, dose rate 4.4 x 10(-6) Gy/h). It was shown that more expressed kinetic anticooperativity of nucleotidase reaction in irradiated animals, as compare to control ones, was conditioned by composition predominance of low-affinity 5'-nucleotidases forms over their high-affinity patterns. The ratio of maximal velocities of high- to low-affinity 5'-nucleotidases was ranged from 2 in the control to 7 in irradiated rats at different postirradiation periods during the first 90 days of observation. It was suggested that appearance of new kinetic 5'-nucleotidases forms in blood stream of irradiated animals, predominantly with low-affinity, was attributed to impairment in the integrity of cellular membranes and may testify to postirradiation development of tissues injury.