RESUMO
Organ of Corti's outer hair cells are one of the few cell types in mammals to contain large cytoplasmic glycogen stores, and the only one in the adult auditory receptor. Previous reports on the structure and distribution of glycogen in the adult organ of Corti were mainly based on light microscopy histo- and cytochemical methods, and the scare EM studies on the topic relied on techniques which were not sensitive or specific enough. Furthermore, it has been reported that glycogen particles are not present in outer hair cells of all species. A first goal of the present study was to describe the ultrastructure of glycogen stores in organ of Corti's outer hair cells in Guinea pig, rat, and mouse, using the periodic acid-thiocarbohydrazide-silver proteinate method. In addition, differences in the subcellular and cochleotopic distribution of this substance were analyzed. In the adult organ of Corti only the outer hair cells contain glycogen stores. Present throughout their cytoplasm, these deposits appear either as single beta particles, or as aggregates of these, forming alpha particles. Though most alpha particles are round, some appear long and conspicuously straight in longitudinal sections of those cells near the apex of the cochlea, and they seem to be apposed to some filamentous structure. On the other hand, when the cells are sectioned transversely the larger aggregates of glycogen particles follow a curved course. Since outer hair cells of the apical region of the cochlea contain a bundle of contractile microfilaments, our results suggest that glycogen is associated with the contractile apparatus of these cells. This hypothesis is in good accordance with previous experimental data which suggest that glycogen is used as energy source for the contractile movements of outer hair cells.