[Changes of Ca(2+)-ATPase in the cochlea of guinea pig during labyrinthine hydrop]

To investigate the localization of Ca(2+)-ATPase (Ca2+ pump) in the cochlea and its change in labyrinthine hydrops.

The left endolymphatic sac was ablated to induce endolymphatic hydrops in fourteen healthy guinea pigs after the sliver ball electrode was placed on the round window. The Ca(2+)-ATPase was studied by the lead citrate reaction in the control and hydropic ears. The reaction product was lead phosphate particles as an expression of Ca(2+)-ATPase activity under the electron-microscope.

The Ca(2+)-ATPase activity was found mainly on the endolymphatic surface of the Reissner's membrane, the stereocilia and cuticular plate of inner and outer hair cells, as well as along the infolding plasma membrane of the strial intermediate cells. The Ca(2+)-ATPase activity was significantly decreased during endolymphatic hydrops in the above-mentioned locations.

The response thresholds of filtered click were increased and the Ca(2+)-ATPase significantly decreased in the cochlea during labyrinthine hydrops. These results suggest that correlation exists between the CAP threshold and the activity of Ca(2+)-ATPase in the model of labyrinthine hydrops.