Changes in the connective tissue composition of the submucosal layer of colonic anastomosis. An immunohistologic study in rats.

Submucosal healing of colonic anastomosis was studied in rats. The unprepared sigmoid colon was divided and colo-colostomy performed, using a one-layer inverting technique. Frozen sections were studied immunohistologically with specific antibodies to fibronectin, laminin and collagen types I, III, IV and V. From the first to the fifth postoperative day the submucosa was highly oedematous. A clear fibronectin reaction was observed in the submucosa, reaching maximum on postoperative day 5. From day 3 onwards the fluorescence intensities of types I and III collagen in the young granulation tissue and of types IV and V collagen and laminin in the regenerating capillaries rapidly increased, with maximum on day 7. The striking changes in the submucosa indicate that the healing process involves not only the actual area of the anastomosis, but also widely the submucosal layer of the adjacent intestine.