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

BACKGROUND: Hydrogen sulfide (H2 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 H2 S production was measured by the methylene blue assay. The expression of DAO was investigated by Western blotting and immunohistochemistry. The short-circuit current (Isc) was recorded using the Ussing chamber technique. KEY RESULTS: The epithelium in rat jejunum possesses DAO, and generates H2 S. D-cysteine, originally used as a negative control for L-Cys, significantly increases the H2 S release, which is inhibited by I2CA, an inhibitor of DAO. In vitro study by Ussing chamber technique reveals that D-Cys decreases the Isc across the epithelium of the rat jejunum and enhances the Na(+) -coupled L-alanine transport. CONCLUSIONS & INFERENCES: A novel pathway for the production of H2 S by DAO exists in rat jejunum.