Changes in activity of cytochrome oxidase in the cochleae of guinea pigs with experimental endolymphatic hydrops.

Cochlear dysfunction may indicate inadequate generation of intracellular metabolic energy which is necessary for the regulation of the transport of ions and fluid as well as production of electro-energy in the cochlea. Changes in cochlear function in the early stages of endolymphatic hydrops attributed to dysfunction of the sensory hair cells and stria vascularis were investigated. The main source of metabolic energy, produced by intracellular respiration, is located in the stria vascularis and sensory hair cells. Since cytochrome oxidase is one of the most important respiratory enzymes, vibratome sections of hydropic and normal cochleae were stained cytochemically for cytochrome oxidase activity in this study. Decreased activity of this enzyme was consistently shown in the normal-appearing outer hair cells and stria vascularis, as well as the degenerated hair cells and stria vascularis, of the higher turns of the hydropic cochlea. The results coincide with those in other studies of electrophysiologic changes in cochlear function in hydropic animals. A decrease in the activity of respiratory enzymes was noted before the destruction of the cellular structures. The activity of cytochrome oxidase may serve as a useful indicator for demonstrating the functional status of cochlear hair cells and stria vascularis.