A novel pathway for the production of H2S by DAO in rat jejunum

Background Hydrogen sulfide (H 2 S) is endogenously generated from L-cysteine (L-Cys) by the enzymes cystathionine- β -synthase (CBS) and cystathionine- γ -Lyase (CSE). Hydrogen sulfide is also produced from D-cysteine (D-Cys) by D-Amino acid oxidase (DAO). Methods The H 2 S production was measured by the methylene blue assay. The expression of DAO was investigated by Western blotting and immunohistochemistry. The short-circuit current ( I sc) was recorded using the Ussing chamber technique. Key Results The epithelium in rat jejunum possesses DAO, and generates H 2 S. D-cysteine, originally used as a negative control for L-Cys, significantly increases the H 2 S release, which is inhibited by I2CA, an inhibitor of DAO. In vitro study by Ussing chamber technique reveals that D-Cys decreases the I sc across the epithelium of the rat jejunum and enhances the Na + -coupled L-alanine transport. Conclusions & Inferences A novel pathway for the production of H 2 S by DAO exists in rat jejunum.