title: [Post-radiation changes in kinetic parameters of purine-catabolizing enzymes in rat blood serum after combined action of external and internal irradiation caused by 137Cs].
abstract: Kinetic parameters (Vmax, Km) of enzymes catalyzing the reaction sequence 5'-AMP-->adenosine-->inosine-->hypoxanthine in rat's blood serum were studied at different postirradiation terms after combined effect of external gamma-irradiation (1 Gy, 137Cs) and incorporated 137Cs (160 kBq). It was shown that radiation-induced changes of kinetic properties of 5'-nucleotidase, adenosine deaminase, purine nucleoside phosphorylase were expressed at earlier terms under combined radiation effect than it occurred at external gamma-irradiation effect only. Postirradiation modification of enzymes kinetics brought about the acceleration of 5'-AMP conversion to its endpoint product, hypoxanthine. Negative consequences of the postirradiation activation of purine metabolism, in particular, the activation of hypoxanthine prooxidant system and the rise of clastogenic activity of blood plasma are discussed.
authors.affiliation: Institute of Radiobiology, National Academy of Sciences of Belarus, Minsk 210141 Belarus. irb@radbio.bas-net.by
authors.forename: S M
authors.initials: SM
authors.lastname: Iakubovskiĭ
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes; D004798:Enzymes / Q000097:blood / Q000528:radiation effects*; D007700:Kinetics; D008297:Male; D011687:Purines / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002588:Cesium Radioisotopes; D004798:Enzymes; D011687:Purines