Characterization of sodium transport in gustatory epithelia from the hamster and rat

The transduction of sodium salts occurs through a variety of mechanisms,including sodium influx through amiloride-sensitive sodium channels,anion-dependent sodium movement through intercellular junctions andunidentified amiloride-insensitive mechanisms. Characterizations of sodiumtransport in lingual epithelium mounted in Ussing chambers have focusedalmost exclusively on epithelia containing only fungiform taste buds. Inthe present study we have investigated sodium transport by measuringNaCl-induced short-circuit current from lingual epithelia containingfungiform, foliate, vallate and palatine taste buds in the hamster and therat. All areas show measurable sodium transport, yet significantdifferences were noted between the epithelia from the rat and the hamsterand among the different epithelia within a single species in terms ofcurrent density, transepithelial resistance and mucosal amiloridesensitivity. In general, epithelia from the anterior tongue were of a lowerresistance and transported sodium more effectively than from the posteriortongue. Moreover, fungiform- and vallate-containing epithelia in the rathad a greater current density than did the corresponding tissues in thehamster. Amiloride sensitivity also differed between the rat and thehamster. In the hamster all gustatory areas showed some amiloridesensitivity, while in the rat the vallate-containing epithelia were devoidof amiloride- sensitive sodium transport. The results are consistent withthe interpretation that all chemosensitive areas may participate in thedetection of salts but the degree of salt transport and the mechanism oftransport is variable among different lingual epithelia and differentspecies.