A Role of the Epithelial Sodium Channel in Human Salt Taste Transduction?

Abstract

Mammals perceive the five different taste qualities: bitter, sweet, umami, sour, and salty. At least two different mechanisms contribute to salt taste in rodents. One is elicited by various cations and sensitive to cetylpyridinium chloride, whereas another is selectively stimulated by Na + and inhibited by amiloride. The latter pathway has been suggested to involve the epithelial sodium channel, ENaC. In humans, the presence of amiloride-sensitive salt taste transduction is being disputed. In this paper, we addressed the question whether ENaC may have a role in human salt taste perception. Immunohistochemistry revealed that β-, γ-, and δ-ENaC subunits are present in subsets of circumvallate and fungiform taste bud cells, whereas α-ENaC was confined to cells of circumvallate taste buds. Alpha-, β-, and γ-subunits were observed in basolateral intracellular compartments, while δ-ENaC was exclusively found in all taste pores of both types of papillae consistent with a function in taste transduction. To further assess the involvement of ENaC in salt taste transduction, we combined sensory studies and functional expression of ENaC in oocytes. With the exception of L-homoarginine, choline chloride, L-arginine, L-lysine, and L-argininyl-Larginine enhanced both salt taste perception in subjects and sodium currents recorded in αβγ-or δβγ-ENaC expressing oocytes, whereas L-glutamine did neither show salttaste-enhancing activity nor did it influence the sodium currents in the oocyte assay. Taken together, our data make ENaC an interesting molecule possibly involved in salty taste transduction.

International Union of Basic and Clinical Pharmacology. XCI. Structure, Function, and Pharmacology of Acid-Sensing Ion Channels and the Epithelial Na+Channel

“…Another sensing system is activated by lower concentrations of Na + and inhibited by amiloride, suggesting the contribution of ENaC in salt taste. In humans, a, b, g, and d ENaC subunits are expressed in taste bud cells (Stahler et al, 2008). In mice lacking a ENaC in taste receptor cells, the highly sensitive response to Na + salt and the behavioral attraction to sodium salt were considerably reduced (Chandrashekar et al, 2010).…”

Genetics of Taste and Smell

“…112 Evolutionary forces may have shaped the human ability to recognize salty taste in such a way as to make it very responsive to differences in the environmental mineral and water supply or habitual diet. 113 Therefore, efforts to assess the impact of genetic variation within the salt receptor 114,115 should focus on salt perception of people with similar environmental backgrounds (e.g., early exposure, recent exposure) and be attentive to the current state of the subject (e.g., time of day, thirst).…”

Heritable differences in chemosensory ability among humans

“…The sodium channel epithelial Na + channel (ENaC) and its subunits are implicated in salt perception in mice and rats [76], but the evidence supporting the involvement of this gene and its protein products in human salt perception is equivocal [77]. Genetic studies of threshold for sodium chloride suggest little genetic involvement [74,78], but studies of intensity ratings of concentrated solutions have shown a moderate degree of heritability (Knaapila et al, submitted).…”