title: Amiloride-sensitive NaCl taste responses are associated with genetic variation of ENaC alpha-subunit in mice.
abstract: An epithelial Na(+) channel (ENaC) is expressed in taste cells and may be involved in the salt taste transduction. ENaC activity is blocked by amiloride, which in several mammalian species also inhibits taste responses to NaCl. In mice, lingual application of amiloride inhibits NaCl responses in the chorda tympani (CT) gustatory nerve much stronger in the C57BL/6 (B6) strain than in the 129P3/J (129) strain. We examined whether this strain difference is related to gene sequence variation or mRNA expression of three ENaC subunits (alpha, beta, gamma). Real-time RT-PCR and in situ hybridization detected no significant strain differences in expression of all three ENaC subunits in fungiform papillae. Sequences of the beta- and gammaENaC subunit genes were also similar in the B6 and 129 strains, but alphaENaC gene had three single nucleotide polymorphisms (SNPs). One of these SNPs resulted in a substitution of arginine in the B6 strain to tryptophan in the 129 strain (R616W) in the alphaENaC protein. To examine association of this SNP with amiloride sensitivity of CT responses to NaCl, we produced F(2) hybrids between B6 and 129 strains. Amiloride inhibited CT responses to NaCl in F(2) hybrids with B6/129 and B6/B6 alphaENaC R616W genotypes stronger than in F(2) hybrids with 129/129 genotype. This suggests that the R616W variation in the alphaENaC subunit affects amiloride sensitivity of the ENaC channel and provides evidence that ENaC is involved in amiloride-sensitive salt taste responses in mice.
authors.affiliation: Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan.
authors.forename: Noriatsu
authors.initials: N
authors.lastname: Shigemura
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Ohkuri
authors.forename: Chiharu
authors.initials: C
authors.lastname: Sadamitsu
authors.forename: Keiko
authors.initials: K
authors.lastname: Yasumatsu
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Yoshida
authors.forename: Gary K
authors.initials: GK
authors.lastname: Beauchamp
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Bachmanov
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Ninomiya
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D002814:Chorda Tympani Nerve / Q000187:drug effects* / Q000502:physiology; D053503:Epithelial Sodium Channels / Q000235:genetics* / Q000378:metabolism; D005260:Female; D007668:Kidney / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects* / Q000502:physiology; D014059:Tongue / Q000378:metabolism
chemical_list: D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D026941:Sodium Channel Blockers; D012965:Sodium Chloride; D000584:Amiloride