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 microliter/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 H2 35S 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.