Background: Studies on muscle contraction in colitis yield conflicting data that may reflect differences in the manner in which colitis is induced. Therefore, we compared distal colonic longitudinal muscle contraction in four models of colitis in the rat.
Methods: Distal colitis was induced by intrarectal administration of trinitrobenzene sulfonic, acetic acid, or Trichinella spiralis larvae, or by intraperitoneal injection of mitomycin C. Colonic myeloperoxidase activity was used to monitor acute inflammation.
Results: Myeloperoxidase activity increased in each model of colitis. In trinitrobenzene-treated rats, contractile responses to carbachol, substance P, and KCl decreased by 64%, 76%, and 58%, respectively. In acetic acid treated rats, responses induced by carbachol, substance P, or KCl were each significantly decreased by 73%, 68%, and 55% and were similarly reduced by 42%, 77%, and 46%, respectively, in rats with T. spiralis colitis. In mitomycin-induced colitis, these respective responses also decreased significantly by 71%, 55%, and 54%.
Conclusion: Decreased contractility of longitudinal muscle in acute colitis in rats is independent of the manner in which the colitis is induced and is mediated at a receptor-independent locus on the muscle cell.