PROCEEDINGS |
Neurotransmitters, hormones and other ligands effect cellular responses on binding to a surface receptor. The ligand bound receptor stimulates PLC which hydrolyzes phosphotidylinositol 4,5-biphosphate to diacylglycerol and inositol trisphosphate, thereby activating protein kinase C and releasing Ca2+ from intracellular stores. Producing second messengers that mediate transmembrane signaling, PLC affects the degree and duration of cell responses. The possibility that PLC contributes to transmembrane signaling in the vestibular organ was investigated here by immunostaining the gerbil vestibule for PLC isozymes.
The inner ears of young adult gerbils were fixed by transcardial and perilymphatic perfusion with zinc-formalin solution. The dissected inner ears were decalcified with EDTA, dehydrated, embedded in paraffin, sectioned and immunostained. Gerbil retina, brain and kidney served as a positive control. Antibodies to eight different isozymes of PLC were tested. The several isoforms were expressed differentially in the various cell-types of the gerbil vestibular system. PLC-beta 1 was detected in macula, transitional epithelium, fibrocytes and ganglion cells in the vestibular system and in selected neurons and nerve tracts in brain and plexi form layer in retina. Antibody to PLC-beta 2 isoform bound to the macula, saccular membrane, dark cells, fibrocytes and ganglion cells in the vestibule and collecting duct in kidney. The beta 3 isozyme was localized to the saccular membrane, dark cells and transitional epithelium, and to retina photoreceptors. PLC-gamma 2 was expressed in the macula and saccular membrane. The localization of PLC -gamma 1 resembled that of PLC-beta 2. PLC-beta 4, -delta 1 and -delta 2 failed to stain the vestibule. When the results in the vestibular system were compared with those in the cochlea, the staining was similar for saccular membrane in the vestibular system and Reisnner's membrane in the cochlea, and for transitional epithelium next to a crista ampulla in the vestibule and Hensen's cells in the cochlea.
These results demonstrate the complexity of PLC distribution in the vestibular organ and suggest that the several isozymes affect the neural and humoral regulation of the various epithelial cell types in different ways.