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Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322
3To whom correspondence should be addressed at Rollins Research Center, Room 4131, 1510 Clifton Road NE.
The control of luminal thiol-disulfide redox state may be important
for several intestinal functions, including absorption of iron or
selenium and maintenance of mucus fluidity. Disulfides are present in
the diet, and although luminal thiols are supplied in bile, little is
known about the ability of the small intestine to reduce disulfides to
maintain the luminal thiol-disulfide redox state. The objective of
the current study was to determine whether the isolated, vascularly
perfused jejunum, free from biliary thiols, could reduce intraluminal
glutathione disulfide (GSSG) to glutathione (GSH). GSSG was introduced
in a deoxygenated solution to inhibit the reoxidation of any GSH
formed, and preparations were pretreated with acivicin to inhibit the
degradation of GSH by 
-glutamyltransferase. GSSG (250 µmol/L) was
reduced to GSH, with the luminal redox potential (Eh) for
GSSG/2GSH changing from >0 to -111, -132 and -143 mV at 10, 20 and
30 min, respectively. The Eh for luminal cystine/2cysteine
was 
20 mV more reducing than that for GSSG/2GSH at each time point,
suggesting that cysteine could function in the reduction of GSSG in the
lumen. Measurements in specific regions showed that GSSG reduction was
more rapid in the duodenum and proximal jejunum than in the distal
jejunum. Preparations without acivicin treatment showed that
Eh values were unaffected by inhibition of
-glutamyltransferase despite differences in GSH and cysteine pool
sizes. Rat intestine has a mechanism to adjust the luminal
thiol-disulfide redox. In principle, dysfunction of this mechanism
could contribute to malabsorption or other nutritional disorders.
KEY WORDS: • glutathione • cysteine • redox • small intestine • rats
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