Neutrophil depletion prevents intestinal mucosal permeability alterations in burn-injured rats

Cutaneous thermal injury increases intestinal mucosal permeability. The mechanisms of this functional disturbance are not fully understood. We investigated whether accumulation of neutrophils in the intestine contributes to the increase in mucosal permeability. Labeled and unlabeled lactulose and mannitol were infused into a segment of rat ileum or jejunum. Blood concentrations of [H-3]lactulose and [C-14]mannitol were measured after 30, 60, and 90 min. On day 1 postburn, lactulose permeability increased fourfold in the ileum and twofold in the jejunum compared with sham-burned rats; mannitol permeability increased twofold in the ileum and 1.5-fold in the jejunum. A greater increase in permeability occurred on day 3 postburn in the ileum, but not in the jejunum. The depletion of neutrophils in burned rats prevented the increase in permeability in both segments on day 1 postburn. Histological studies of intestines from burned, with or without neutrophil depletion, and sham-burned rats showed similar morphology. However, numerous neutrophils were found in the extravascular compartment in day 1 postburn, but not in neutrophil-depleted and sham-burned rats. These findings support the concept that the burn-induced increase in mucosal permeability is produced during the accumulation of neutrophils in the intestine and can be abrogated by the depletion of neutrophils.