DIFFERENTIAL EXPRESSION OF ALPHA-GUSTDUCIN IN TASTE BUD POPULATIONS OF THE RAT AND HAMSTER

The G-protein subunit alpha-gustducin, which is similar to rod transdu cin, has been implicated in the transduction of both sweet- and bitter -tasting substances. In rodents, there are differences in sensitivity to sweet and bitter stimuli in different populations of taste buds. Ra t fungiform taste buds are more responsive to sails than to sweet stim uli, whereas those on the palate respond predominantly to sweet substa nces, In contrast, hamster fungiform taste buds are more sensitive to sweet-tasting stimuli. Taste buds in the vallate and foliate papillae of both species are sensitive to bitter compounds. These differences i n sensitivity should be reflected in the numbers of gustducin-containi ng cells in different taste bud populations. We examined taste buds in the rat and hamster for immunoreactivity to an antibody against alpha -gustducin. Immunofluorescence of labeled taste cells was examined by confocal microscopy, and the cells were counted. Gustducin-positive ce lls were seen in all taste bud regions; they were spindle-shaped, with circular cross-sections and apical processes that extended to the tas te pore. Cells with this characteristic shape in rat vallate taste bud s are Type II (light) cells, In the rat, taste buds of the fungiform p apillae had fewer gustducin-positive cells (3.1/taste bud) than those of other regions, including the posterior tongue and palate (>8.9/tast e bud). Hamster fungiform taste buds contained twice as many gustducin -expressing cells (6.8/taste bud) as those of the rat. These data supp ort the hypothesis that alpha-gustducin is involved in the transductio n of both sweet- and bitter-tasting stimuli by mammalian taste recepto r cells.