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

Cutaneous thermal injury increases intestinal mucosal permeability. The mec hanisms of this functional disturbance are not fully understood. We investi gated whether accumulation of neutrophils in the intestine contributes to t he increase in mucosal permeability. Labeled and unlabeled lactulose and ma nnitol were infused into a segment of rat ileum or jejunum. Blood concentra tions 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, b ut not in the jejunum. The depletion of neutrophils in burned rats prevente d the increase in permeability in both segments on day 1 postburn. Histolog ical studies of intestines from burned, with or without neutrophil depletio n, and sham-burned rats showed similar morphology. However, numerous neutro phils were found in the extravascular compartment in day 1 postburn, but no t in neutrophil-depleted and sham-burned rats. These findings support the c oncept that the burn-induced increase in mucosal permeability is produced d uring the accumulation of neutrophils in the intestine and can be abrogated by the depletion of neutrophils.