Effect of kokumi taste-active γ-glutamyl peptides on amiloride-sensitive epithelial Na+ channels in rat fungiform taste cells

Kokumi taste-active compounds enhance salty taste perception. In animal models, sodium (salt) detection is mediated by the amiloride-sensitive epithelial sodium channel, ENaC. This ion channel works as a sodium receptor in the so-called sodium-taste cells. It is not known whether kokumi taste substances are able to affect the activity of functional ENaCs in these cells. Here, we use the patch-clamp technique to study the effect of kokumi-active tripeptides, glutathione (GSH) and γ-glutamyl-valyl-glycine (EVG), on the ENaC-mediated membrane current in rat fungiform sodium-taste cells. GSH and EVG reduced slightly this current and the effect disappeared in the presence of amiloride, a specific ENaC blocker. No effect on membrane current was detected in other taste cells (Type II and Type III cells) that do not express functional ENaC. Our findings suggest that the enhancing effect of kokumi taste-active γ-glutamyl peptides on salt reception is not explained by an increase in the activity of ENaC.