Acid enhances salt taste by activating the epithelial sodium channel

Salt is often used to enhance the flavor of foods and drinks, and in turn, some foods and drinks may intensify the taste of salt. For example, highly acidic carbonated beverages sometimes accompany salty snacks, and margaritas made with acidic citrus are served in salt-rimmed glasses. However, whether and how acid might enhance salt taste remain unknown. Epithelial sodium channels (ENaC) in tongue taste cells detect dietary sodium. We found that acid irreversibly increased ENaC channel activity, with half-maximal activation occurring at pH 2.6. Acid altered ENaC gating by increasing the rate of channel opening and reducing the rate of channel closing. Acidic beverages Coca-Cola(R) and Pepsi(R) (pH 2.2-2.4) also stimulated ENaC current but Diet Coke(R) (pH 3.2) did not. In humans, we found that acid reduced the sodium taste detection threshold. These findings identify a functional interplay between dietary sodium and acid--by modulating ENaC gating, acid enhances salt taste.