Abstract
Amiloride, a epithelial Na+ channel bloker, is known to inhibit responses to NaCl of taste cells and the chorda tympani (CT) nerve innervating the anterior tongue in various mammalian species. In mice, amiloride sensitivity varies among strains; C57BL/6 (B6) mice exhibited inhibition of NaCl responses by amiloride to -50% of control, whereas NaCl responses were only slightly inhibited by amiloride (-20% of control) in 129P3/J (129) mice. The amiloride-sensitive epithelial Na+ channel (ENaC) expressed in taste cells is a potent candidate to play a role in the salt responses. In this study, using amiloride-sensitive B6, amiloride-weakly sensitive 129 strains and their F2 hybrids, we investigated possible relationships of the amiloride sensitivity with single nucleotide polymorphisms (SNPs) of three subunits of ENaC (α, β, γ) in the anterior tongue. The results showed that sequencing detected a SNP resulted in an amino acid substitution, R616W in αsubunit. No SNP was found in β and γsubunits. F2 hybrid mice were divided into 3 groups according to their αENaC R616W genotypes (129/129, B6/129 and B6/B6). Responses of the CT nerve to 0.03-0.3 M NaCl decreased after amiloride treatment in B6 and F2 (B6/129 and B6/B6), whereas only weak inhibition was evident in 129 and F2 (129/129). These results suggest that R616W of ENaC αsubunit may be one of factors responsible for mouse strain differences in amiloride sensitive salt responses. [J Physiol Sci. 2007;57 Suppl:S103]
