Solubility of tissue hydroxyproline in experimental intestinal anastomoses.

Salt and acid solubility of collagen are thought to reflect its degree of crosslinking. In order to examine postoperative changes in crosslinking of intestinal collagen, which are of importance to the stability of the intestinal wall, we have investigated the solubility of hydroxyproline in rabbit ileum and colon, both in unwounded intestine and after construction of an anastomosis. Solubility in salt and dilute acid was increased by a sonication procedure. This way, 9% of total hydroxyproline in the unwounded colonic wall was salt soluble and 65% acid soluble. A similar distribution was observed in ileum. Three days after operation the salt-soluble fraction was significantly elevated in samples from the anastomotic area. In colon, this increase also persisted 7 days postoperatively. Comparison of anastomotic samples collected 3 and 7 days after surgery shows a significant decrease in the acid-soluble and a significant increase in the solid fraction. This phenomenon occurs both in ileum and colon. These results indicate that during the first days after operation the integrity of the intestinal wall is weakened not only by a loss of collagen, but also by a changed solubility of the remaining collagen.