Hydrogen sulfide production and detoxification in the colon

Potentially toxic quantities of H₂S are produced by the colonic bacteria of man and animals. Damage to the colonic mucosa and possibly systemic toxicity would be expected if the colonic mucosa did not have an efficient means of detoxifying this H₂S. While this detoxification was thought to take place via demethylation, we recently demonstrated that the normal cecal mucosa rapidly oxidizes H₂S to form thiosulfate. There is a body of evidence that suggests that excessive colonic sulfide production plays a role in colonic diseases such as ulcerative colitis. The possibility also exists that a defect in H₂S oxidation could play a role in various forms of colitis. The ability of poorly absorbed bismuth preparations (such as bismuth subsalicylate) to markedly reduce H₂S release from fecal material may explain the therapeutic benefit reported with the use of bismuth in various forms of colitis.