MEASUREMENT OF [CA2-CELLS ISOLATED FROM GERBIL COCHLEA(](I) AND [NA+](I) IN OUTER HAIR)

Outer hair cells (OHCs) become sodium-and calcium-overloaded after bei ng isolated in high-sodium medium. Most of the sodium and calcium leak occurs through 10-15% of the transduction channels that are open at t he resting position of the hair bundle. However, [Ca2+](i) and [Na+](i ) in OHCs can vary greatly from cell to cell even though they all appe ar normal. Different [Ca2+](i) and [Na+](i) may result from different leak conductance through the transduction channels. The leak was deter mined by the degree of damage inflicted upon the tip-link of the hair bundle during isolation. Excessive sodium accumulation may explain why OHCs cannot maintain their normal resting membrane potential in some experimental conditions.