Intracellular calcium increase in gerbil taste cell by amino acid sweeteners

Gustatory transduction mechanisms for sucrose and amino acid sweeteners in gerbil taste cells were studied with Ca2+ imaging and whole cell recording techniques. A 100 mM sucrose stimulus with Ca2+ increased the intracellular Ca2+ concentration ([Ca2+]i) in sweet-sensitive taste cells of the taste bud, but the sucrose stimulus without Ca2+ did not change the [Ca2+]i. A 10 mM D-phenylalanine sweet stimulus with or without Ca2+ similarly increased the [Ca2+]i in the taste bud. The addition of 5 microM ionomysin, a Ca(2+)-ionophore, without Ca2+ greatly increased the [Ca2+]i in the taste bud. The application of 10 mM D-phenylalanine stimulus without Ca2+ enhanced the outward K+ current in isolated taste cells. These results suggest that a sugar sweetener such as sucrose induces a depolarization in gerbil taste cells which activates voltage-dependent Ca2+ channels and that a non-sugar sweetener such as D-phenylalanine releases Ca2+ from the internal stores without a depolarization.