The effect of a taurine modified diet on normal and hydropic ears of the guinea pig

Immunoreactivity for taurine in the cochlea: its abundance in supporting cells

Taurine is the second most abundant free amino acid in the brain where its osmoregulatory function is well established. Taurine-deprived kittens show retinal pathology leading to blindness. In the inner ear, taurine has been reported to be the most abundant free amino acid although its role in inner ear function is not known. Immunohistochemistry was employed here to investigate the localisation of taurine in normal cochleae of the guinea pig compared with two different conditions: experimentally induced endolymphatic hydrops and after oral administration of glycerol. In normal cochleae, by light microscopy, taurine-like immunoreaction was never observed in the sensory outer hair cells and appeared absent from the inner hair cells. In contrast taurine-like immunolabeling was found to be present in all supporting tissue with the striking exception of the tectorial membrane and the outer pillar cell which had no or little taurine immunoreactivity respectively. In early experimental endolymphatic hydrops, the distribution of taurine-like immunoreactivity appeared similar to that observed for normal cochleae. In long-term hydrops, degenerated outer hair cells were replaced by the swelling of the phalangeal process of the Deiters' cells which became highly immunoreactive to taurine. After glycerol administration, the tectorial membrane became more tightly bound to the apical surface of the sensory hair cells and distinctly immunoreactive to taurine. The localisation of taurine in the organ of Corti shown here is consistent with taurine being involved in the maintenance of osmotic equilibrium in the normal and perhaps also in the restructuration of the pathological organ of Corti.

The localization of taurine-like immunoreactivity in the organ of Corti: a semiquantitative, post-embedding immuno-electron microscopic analysis in the rat with some observations in the guinea pig

The cellular and subcellular localization of taurine in the organ of Corti was examined by means of postembedding immunocytochemistry. Supporting cells, including border cells, inner phalangeal cells, Deiters cells, pillar cells, and Böttcher cells are enriched in taurine-like immunoreactivity, contrasting sharply with inner and outer hair cells which did not show noteworthy immunolabelling. Immunogold cytochemistry indicated an even distribution of taurine throughout the cytoplasm and karyoplasm of the labelled supporting cells. Rats and guinea pigs showed similar labelling patterns. The present immunocytochemical findings indicate that supporting cells are the plausible sources of the reported potassium-induced taurine release in the cochlea. The distribution of taurine in the organ of Corti is not compatible with a transmitter or neuromodulatory action of this amino acid, but rather suggests an involvement in osmoregulatory functions.