Contractility in vitro and mitochondrial response in small and large rabbit bowel after anastomosis

Leakage of a large bowel anastomosis remains the most serious postoperative complication in gastrointestinal surgery. In a recent experimental study we found that surgically induced hypoxia resulted in more derangement of a variety of biochemical markers in the large bowel (LB) than in the small bowel (SB). We explored the question of whether spontaneous and agonist-induced contractility of SB and LB muscle strips was influenced by surgical procedures and how contractility was related to energetic oxidative metabolism capacity in smooth muscle mitochondria. Sixty male New Zealand rabbits were operated on under general anesthesia. Segments of ileum and colon were resected from each rabbit, and an end-to-end anastomosis was constructed. A representative subset of segments from SB (n = 14) and LB (n = 14) at time 0 was used as controls. Tracts containing an anastomosis were resected at days 2, 7, and 14 after operation. At each time point, 20 segments adjacent to the anastomosis of both SB and LB were used for tensiometric and biochemical studies. Tensiometric studies demonstrated modifications in the smooth muscle function at both the acute and chronic stages with intestinal inflammation that may contribute to surgical stress-associated abnormal motility. Biochemical data showed that the respiratory capacity of the resected LB was more impaired than that of the SB. In both SB and LB, changes in respiratory activity preceded tensiometric changes. Thus abnormalities of contractility after surgical stress are more evident in LB than SB in segments adjacent to the anastomoses. This could be the consequence of abnormal biochemical changes, as adenosine triphosphate (ATP) is required for membrane potential maintenance, calcium homeostasis, and actin-myosin interactions.