Immunohistochemical localization of phospholipase C isozymes in mature anddeveloping gerbil cochlea

The possibility that phospholipase C contributes to intracellular signaling in the cochlea was investigated by immunostaining for eight different isof orms of the enzyme. In the mature gerbil cochlea, expression of the isozyme s varied widely among different cell types. The phospholipase C-beta1 isofo rm was detected in inner and outer hair cells. and spiral ganglion neurons where it may participate in regulating Ca2+ flux. The beta3 isozyme was exp ressed in epithelial cells thought to mediate lateral and medial circulatio n of potassium. The beta2 isozyme was present in border, inner phalangeal a nd Hensen cells, the stria vascularis, and suprastrial and supralimbal fibr ocytes where it also may be involved in regulating ion transport activities . The phospholipase C-gamma isozymes were expressed in supporting cells, th e stria vascularis, and certain fibrocytes where they possibly participate in activating tyrosine kinase and modulating ion conductances. The delta2 i soform was found in pillar, outer sulcus and strial marginal cells as well as spiral ganglion neurons and their radial processes. Documentation of cha nges in the expression pattern of phospholipase C isoforms during postnatal development and knowledge of their distribution in several positive contro l tissues provided further data for speculation about the biologic signific ance of the cochlear reactivity. The results demonstrate a wide diversity o f isozyme distribution in the cochlea and suggest that the enzymes affect a ctivities of various cochlear cell types in different ways. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.