Role of neutrophils in ischemia-reperfusion-induced microvascular injury.

Recent studies indicate that polymorphonuclear neutrophils (PMNs) infiltrate the intestinal mucosa during ischemia and after reperfusion. To determine whether PMNs mediate the increased microvascular permeability produced by ischemia-reperfusion (I/R) we treated cats with either saline, antineutrophil serum (ANS), or a monoclonal antibody specific for the beta-chain of the CD18 complex (MoAb 60.3) that prevents neutrophil adherence and extravasation. Intestinal microvascular permeability to plasma proteins was measured in control preparations (0.08 +/- 0.007), in preparations subjected to 1 h of ischemia then reperfusion (I/R, 0.32 +/- 0.02), I/R preparations treated with ANS (0.13 +/- 0.01), and I/R preparations treated with MoAb (0.12 +/- 0.003). Our results indicate that both PMN depletion (to less than 10% control) and prevention of PMN adherence significantly attenuate the increased microvascular permeability induced by I/R. These findings, coupled to previous results obtained from this model, support the hypothesis that neutrophils, which accumulate in the mucosa in response to xanthine oxidase activation, mediate the oxyradical-dependent injury produced by reperfusion of the ischemic bowel.