We investigated the role of
free radicals, especially from activated neutrophils, in acute
xanthine and
xanthine oxidase-induced
lung injury in rats. We evaluated the effects of intravenously administered intracellular and extracellular
free radical scavengers (for O2-., H2O2, and .
OH),
methylprednisolone (MP), and
Ulinastatin (UST, a
protease inhibitor), on this animal model of
lung injury. At 5 min prior to the intrabronchial injection of a mixture of
xanthine (X, 100 nmol) and
xanthine oxidase (XO, 1 unit) used to induce unilateral lung damage, rats were pretreated intravenously with
superoxide dismutase (SOD, 40 mg/kg), SOD (40 mg/kg) plus
catalase (CAT, 30 mg/kg),
dimethylthiourea (
DMTU, 500 mg/kg), N-2-mercaptopropionyl
glycine (MPG, 20 mg/kg), MP, 30 mg/kg, and UST, 50,000 units/kg. Each scavenger was infused intravenously at one-half the initial dose for 20 min after intrabronchial injection; 3 hr later, we examined the wet/dry lung weight ratios and the levels of
thiobarbituric acid-reactive substances (
TBARS) in lung tissue. Intrabronchial injection of the X/XO mixture markedly increased wet/dry lung weight ratios and lung tissue content of
TBARS. Histopathologic changes were observed in the injected lung as well. Pretreatment with SOD + CAT,
DMTU, and UST significantly reduced the increases in wet/dry lung weight ratios and lung tissue content of
TBARS induced by the intrabronchial injection of the X/XO mixture. Our data suggest indirectly that
free radicals (H2O2, .
OH) and
proteases from activated neutrophils may contribute, in part, to the lung damage induced by the O2-.-generating system of
xanthine and
xanthine oxidase.