ROLE OF XANTHINE-OXIDASE AND NEUTROPHILS IN ISCHEMIA-REPERFUSION INJURY IN RABBIT LUNG

This study evaluated the effect of ischemia-reperfusion (I-R) on pulmonary capillary permeability in isolated rabbit lungs and the roles of xanthine oxidase (XO), aldehyde oxidase (AO), and neutrophils (PMN) in producing this lung injury. Effects of XO and AO were studied by inactivation with a tungsten-enriched diet (0.7 g/kg) and inhibition of XO by allopurinol (100-mu-M) or AO by menadione (3.5-mu-M). PMN effects were studied by preventing endothelial adhesion with the monoclonal antibody IB4 (10-mu-M). Vascular permeability was evaluated by determining the capillary filtration coefficient (K(f,c)) measured before and after I-R in all experimental conditions. Reperfusion after 2 h of ischemia significantly increased pulmonary capillary permeability (K(f,c) changed from 0.096 +/- 0.014 to 0.213 +/- 0.025 ml.min-1.cmH2O-1.100 g-1), and this increase was blocked by the addition of catalase (50,000 U) at reperfusion (baseline K(f,c) was 0.125 +/- 0.023 and 0.116 +/- 0.014 ml.min-1.cmH2O-100 g-1). XO inactivation with the tungsten-supplemented diet and XO inhibition with allopurinol prevented the K(f,c) increase observed after I-R(0.183 +/- 0.030 to 0.185 +/- 0.033 and 0.126 +/- 0.018 to 0.103 +/- 0.005 ml.min-1.cmH2O-1.100 g-1). Inhibition of AO had no effect on I-R injury (K(f,c) 0.108 +/- 0.011 to 0.167 +/- 0.014 ml.min-1.cmH2O-1.100 g-1). Preventing PMN adhesion resulted in significant attentuation of the change in K(f,c) associated with I-R (0.112 +/- 0.032 to 0.090 +/- 0.065 ml.min-1.cmH2O-1.100 g-1). We conclude that XO and PMN adherence, but not AO, are involved in the increased capillary permeability associated with I-R.