Intra-abdominal sepsis impairs colonic reparative collagen synthesis.

BACKGROUND

Intra-abdominal infection is generally considered a contraindication to primary colon anastomosis. In order to elucidate the mechanisms by which sepsis affects colonic healing, we studied anastomotic new collagen and protein synthesis and collagen gene expression in a relevant animal model.

METHODS

Forty male Sprague-Dawley rats (240 to 260 g) underwent sham laparotomy (SHAM, n = 18) or cecal ligation and single puncture (CLP, n = 22). After 24 hours, animals underwent single-layer left colon anastomosis. Animals were sacrificed either 1 or 4 days postanastomosis. Anastomotic segments of colon were excised, minced, and incubated with 4.5 muCi 3H-proline. After 3 hours, tissue 3H-proline incorporation was quantitated as an index of total new protein synthesis. The protein fraction was then digested with purified collagenase enzyme to determine 3H-proline incorporation into collagenase-digestible protein, an index of new collagen synthesis. Total RNA was extracted from anastomotic tissue samples and subjected to Northern blot analysis for type I and type III collagen genes.

RESULTS

Intra-abdominal sepsis resulted in markedly less new collagen synthesis 1 day postanastomosis (9,163 +/- 1,234 versus 3,744 +/- 444 disintegrates per minute 3H-proline/mg of protein, P < 0.0001) and 4 days postanastomosis (8,462 +/- 956 versus 5,708 +/- 802 dpm/mg of protein P < 0.05). Noncollagenous protein synthesis was also impaired in anastomotic tissue from CLP rats on postanastomosis day 1 (37,497 +/- 3,740 versus 18,593 +/- 2,695 dpm/mg of of protein, P < 0.001) and postanastomosis day 4 (28,238 +/- 834 versus 17,784 +/- 1,415 dpm/mg of of protein, P < 0.0001). The expression of type I and type III collagen was altered relative to the normal temporal sequence observed in SHAM animals.

CONCLUSIONS

Intra-abdominal infection impairs colonic reparative collagen and protein synthesis. In addition, regulation of type I and type III collagen genes is altered by intra-abdominal sepsis, and the alteration likely contributes to impaired new collagen synthesis and decreased colonic mechanical strength.