Occurrence of gustducin-immunoreactive cells in von Ebner's glands of guinea pigs

Abstract

An immunohistochemical examination of guinea-pig taste buds in vallate papillae revealed gustducin-immunoreactive cells in the area of von Ebner's glands, minor salivary glands. Since there have been no reports describing those cells in these locations for other species, we investigated these glands in order both to localize the cells and compare their immunoreactive characteristics with corresponding cells in the vallate taste buds. The gustducin-immunoreactive cells coincided with cells containing no secretory granules in the end portion of the glands, which was supported by the electron-microscopic immunocytochemistry. Double immunofluorescence microscopy confirmed these cells to be entirely immunopositive to type III inositol 1,4,5-triphosphate receptor (IP3R-3), phospholipase Cβ2 (PLCβ2), and villin and also partly immunopositive to neuron-specific enolase (NSE) and calbindin D-28K. The gustducin-immunoreactive cells in the vallate taste buds exhibited completely the same immunoreactivities for these five molecules. Accordingly, the present results give credence to a consideration that the gustducin-immunnoreactive cells in both locations are identical in function(s) e.g., chemo-reception.

Fig. 1

a–c Fluorescence-microscopic immunohistochemistry for gustducin in the tongue radix including vallate papillae and von Ebner’s glands. a Immunoreactive cells are discernible not only in the vallate taste buds (upper right) but also in the deeper part of the glands (arrows). b, c Consecutive sections immunostainined with the non-absorbed primary antibody (b) or with the antibody preabsorbed with the corresponding antigen (c). The Fluorescence vanishes from the tissue section immunostained with the preabsorbed antibody (c). Scale bars 50 μm

Fig. 2

a–c Semithin sections of von Ebner’s glands stained with toluidine blue (a, b) or immunostained for gustducin (c). a End portion of the glands. Predominant are the secretory cells accumulating secretory granules in the supranuclear cytoplasm (asterisks). A clear cell intermingles with the secretory cells (arrow). Note that the clear cell lacks secretory granules. b, c Consecutive sections. The clear cells exclusively exhibit the immunoreactivity for gustducin (arrowheads). Scale bars 10 μm

Fig. 3

Electron-microscopic immunocytochemistry for gustducin in von Ebner’s glands. The immunoreactivity is localized in the whole cytoplasm of a cell lacking secretory granules, which is a significant feature of the clear cell. The cell extends from the basement membrane to the apical lumen (asterisk). Scale bar 6 μm

Fig. 4

a–o Laser-scanning microscopic immunohistochemistry for gustducin (a–e) and the others (f–j); overlays of a–e and f–j (k–o) in von Ebner’s glands, respectively. The gustducin-immunoreactive cells are all immunopositive to IP₃R-3 (k), PLCβ2 (l), and villin (m) but only partly immunopositive to NSE (n) and calbindin D-28K (o). Scale bars 10 μm

Fig. 5

a–o Laser-scanning microscopic immunohistochemistry for gustducin (a–e) and the others (f–j); overlays of a–e and f–j (k–o) in vallate taste buds, respectively. The gustducin-immunoreactive cells are all immunopositive to IP₃R-3 (k), PLCβ2 (l), and villin (m) but only partly immunopositive to NSE (n) and calbindin D-28K (o). Scale bars 10 μm