Neutrophil-Induced Decrease in Wound Margin Strength after Intestinal Anastomosis – Influence onCollagen and Mechanisms of Granulocyte Action

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Abstract
A marked decrease in strength occurs early after surgery in tissues adjacent to an incisional wound. In this study measurement of collagen and a histological examination were carired out in a rat intestinal anastomosis. The decrease in tissue strength of the bowel wall did not correlate to the amount of collagen or to changes in collagen solubility. At histology the collagen layer was seen unaffected. Our previous studies showed that the decrease in strength was eliminated if the number of circulating neutrophils was reduced by antineutrophil serum. In addition, the decrease was counteracted by a proteinase inhibitor, the soybean trypsin inhibitor (STI), and the oxygen-free-radical scavengers superoxide dismutase (SOD) and catalase. To further examine the mechanisms of the decrease, neutrophil accumulation in the anastomosis was examined by myeloperoxidase (MPO) assay, and at histology, after treatment of the animals with the proteinase inhibitor, the scavengers or saline solution. MPO activity increased by 110% 24 h after the operation in saline-treated animals, but the increase was not influenced by STI or SOD and catalase. At the histological examination neutrophil accumulation was not seen affected by the drugs. Thus, the proteinase inhibitor and the scavengers counteract the decrease in strength in some other way than by reducing the number of neutrophils in the wound edges, for instance by local inhibition of neutrophil proteolytic enzymes and oxygen-free radicals.