Pulmonary xanthine oxidase activity of rats exposed to prolonged immobilization stress

This study was designed to study xanthine oxidase (XO) and xanthine dehydro genase (XD) activity in the lung of rats expozed to prolonged restraining i mmobilization stress. Immobilization caused more than twofold increase of x anthine oxidase activity in the rat lung. The activity of xanthine oxidase decreased in lung homogenates incubated at -20 degrees C for 24 h. The same incubation of homogenates from control rats caused a non-significant incre ase of the activity. No measurable NAD(+)-dependent xanthine dehydrogenase activity could be established in the lungs of both control rats and rats su bjected to immobilization. All rats revealed methylene blue-dependent xanth ine dehydrogenase activity which was more than two-times higher in the immo bilized animals. Incubation at -20 degrees C for 24 h increased the methyle ne blue-dependent xanthine dehydrogenase activity in homogenates from contr ol rats and decreased the enzyme activity in homogenates from immobilized r ats. A working hypothesis was proposed for the sequence of events explainin g the results obtained: XO - catalyzed generation of activated oxygen speci es may take place in the initiation of lipid peroxidation in the lung of ra ts immobilized for prolonged periods of time.