Allicin Induces Electrogenic Secretion of Chloride and Bicarbonate Ions in Rat Colon via the TRPA1 Receptor

Allicin, an antioxidant from garlic, is known to regulate intestinal contractions, but its effect on intestinal ion transport is unclear. The aim of this study was to examine the role of allicin in the regulation of electrogenic ion transport in rat intestine by measuring the transmural potential difference (ΔPD). Allicin induced significant positive ΔPD, when administered to the serosal side of the colonic mucosal-submucosal preparation. Allicin-induced colonic ΔPD was largely diminished by incubation in the chloride-free solution, although the transient peak of ΔPD after application of allicin remained. This transient peak of ΔPD was significantly diminished in both the chloride- and the bicarbonate-free incubation solution. Induction of ΔPD by allicin was greatly diminished by AP-18, an inhibitor of the transient receptor potential (TRP) cation channel subfamily A member 1, TRPA1. Both alliin and S-allylcysteine, the analogues of allicin, had no effect on ΔPD and did not affect allicin-induced ΔPD in the colon. These results suggest that allicin mainly evokes the electrogenic chloride secretion and only partially increases the electrogenic bicarbonate secretion via TRPA1.