Ionic changes in cochlear endolymph of the guinea pig induced by acoustic injury.
The effects of acoustic overstimulation on the endocochlear potential (EP) and on concentrations of ions (K+, Na+, Cl-, H+, HCO3-, and Ca2+) in endolymph were investigated using ion-selective microelectrodes. A slight but significant elevation of the EP and alkalinization of the endolymph were induced by acoustic overstimulation, whereas there was little change in the K+, Na+, Cl-, and HCO3- concentrations. The changes in H+ and HCO3- concentrations implied a depression of PCO2, suggesting an increase in blood flow to the cochlea. On the other hand, the Ca2+ concentration increased abruptly to 48 times the pre-exposure value. In contrast, no significant change in the Ca2+ concentration was observed in cochleae with damaged hair cells. We discuss the mechanism of the tone-induced Ca2+ elevation in endolymph and its effect on hearing acuity.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003051:Cochlea / Q000187:drug effects / Q000293:injuries* / Q000378:metabolism; D003055:Cochlear Microphonic Potentials / Q000187:drug effects; D004710:Endolymph / Q000378:metabolism*; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007761:Labyrinthine Fluids / Q000378:metabolism*; D008466:Mechlorethamine; D009588:Nitrogen Mustard Compounds / Q000633:toxicity; D009622:Noise / Q000009:adverse effects; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D001639:Bicarbonates; D002712:Chlorides; D007477:Ions; D009588:Nitrogen Mustard Compounds; D008466:Mechlorethamine; D012964:Sodium; D011188:Potassium; D002118:Calcium