ALTERATION OF 5'-NUCLEOTIDASE PROPERTIES IN RAT ADIPOSE AND LIVER PLASMA-MEMBRANES AFTER 1 GY WHOLE-BODY GAMMA-IRRADIATION

5'-Nucleotidase activites in rat adipose and liver plasma membranes (P M) were examined at various times after 1 Gy whole-body gamma-irradiat ion. Changes in the enzyme kinetic parameters were recorded 6 and 14 w eeks after exposure: K(m) decreased while V(max) increased. The enzyme in control PM showed temperature-dependent Arrhenius plots with a low er activation energy at temperatures above a break point at approximat ely 28-degrees-C, whereas 5'-nucleotidase in irradated PM showed a con stant activation energy between 10 and 40-degrees-C which was reasonab ly close to the value observed controls at temperatures below the brea k point. Furthermore, the interaction of [H-3]-AMP with the 5'-nucleot idase catalytic site was studied on adipose PM using a rapid filtratio n technique. Gamma-Irradiation was associated with an increased number of specific AMP-binding sites and decreased ligand affinity. Comparis on of the presented data with previous work (Yegutkin et al. 1993a,b) indicate significant functional and structural modification of rat adi pose and liver PM following 1 Gy gamma-irradiation and reveals interre lation of these changes.