Localization of Ca2+ -stores and tissue compartments with a Ca2+ -binding capacity in the organ of Corti of the guinea-pig by electron energy-loss spectroscopy

Abstract

The addition of 10 mM CaCl₂ to glutaraldehyde fixative leads to the formation of small electron‐dense deposits in the organ of Corti of the guinea‐pig. These precipitates are mainly attached to cell membranes in contact with different extracellular lymphatic fluids. A higher number of precipitates is localized in the acellular parts of tectorial and basilar membrane. Electron energy‐loss spectroscopy (EELS) was used to determine the elemental composition of the deposits formed. The spectra showed a prominent signal at the Ca²⁺ L_2,3 ionization edge. Oxygen could also be detected in all the precipitates analysed. EELS analysis of mitochondria of the inner and outer hair cells after conventional fixation (glutaraldehyde followed by post‐fixation in OsO₄) revealed a small but significant calcium signal.