Production and elimination of sulfur-containing gases in the rat colon

Highly toxic sulfur-containing gases have been pathogenetically implicated in ulcerative colitis. Utilizing a rat model, we studied the production and elimination of sulfur-containing gases within the unperturbed colon. The major sulfur-containing gases were hydrogen sulfide (H₂S), methanethiol, and dimethyl sulfide with cecal accumulation rates of 2.6, 0.096, and 0.046 μl/min, respectively. The dependence of H₂S production on dietary components was demonstrated via a sixfold reduction with fasting and a fivefold increase with carrageenan (a nonabsorbable, sulfur compound) feeding. Zinc acetate reduced cecal H₂S by fivefold, indicating the importance of H₂S binding by divalent cations. During passage from the cecum to the rectum, >90% of the sulfur gases were absorbed or metabolized. An H₂³65S turnover of 97%/min was observed in the isolated cecum. Thus mucosal exposure is >10 times the measured accumulation rate. Cecal mucosal tissue very rapidly metabolized H₂S and methanethiol via a nonmethylating reaction.