J. Furne et al., Oxidation of hydrogen sulfide and methanethiol to thiosulfate by rat tissues: a specialized function of the colonic mucosa, BIOCH PHARM, 62(2), 2001, pp. 255-259
Colonic bacteria release large quantities of the highly toxic thiols hydrog
en sulfide (H2S) and methanethiol (CH3SH). These gases rapidly permeate the
colonic mucosa, and tissue damage would be expected if the mucosa could no
t detoxify these compounds rapidly. We previously showed that rat cecal muc
osa metabolizes these thiols via conversion to thiosulfate. The purpose of
the present study in rats was to determine if this conversion of thiols to
thiosulfate is (a) a generalized function of many tissues, or (b) a special
ized function of the colonic mucosa. The tissues studied were mucosa from t
he cecum, right colon, mid-colon, ileum, and stomach; liver; muscle; erythr
ocytes; and plasma. The metabolic rate was determined by incubating homogen
ates of the various tissues with (H2S)-S-35 and (CH3SH)-S-35 and measuring
the rate of incorporation of S-35 into thiosulfate and sulfate. The detoxif
ication activity of H2S (expressed as nmol/mg per min) that resulted in thi
osulfate production was at least eight times greater for cecal and right co
lonic mucosa than for the non-colonic tissues. Thiosulfate production from
CH3SH was at least five times more rapid for cecal and right colonic mucosa
than for the non-colonic tissues. We conclude that colonic mucosa possesse
s a specialized detoxification system that allows this tissue to rapidly me
tabolize H2S and CH3SH to thiosulfate. Presumably, this highly developed sy
stem protects the colon from what otherwise might be injurious concentratio
ns of H2S and CH3SH. Defects in this detoxification pathway possibly could
play a role in the pathogenesis of various forms of colitis. (C) 2001 Elsev
ier Science Inc. All rights reserved.