Deiters’s cells are one of the types of supporting cells in the cochlear. These cells are supporting the outer hair cells (OHCs) at their base and apex. This structure is thought to be related to the effect of modifying cochlear mechanics by affecting OHCs motion induced by sound. Recently, voltage activated, outward rectifying potassium currents were found in Deiters’ cells and its electrical characteristics were identified (Nenov, Chen & Bobbin, 1998). Even though their study showed the characteristics of K+-currents, we found this K+-current is quite different characteristics from the other ordinary K+ currents. Therefore we tried to identify the characteristics of the K+-current of Deiters’ cells. We isolated Deiters’ cells using collagenase from the cochlear of guina-pig. To record K+-current, whole cell patch clamp technique was applied. With high K+ pipette solution, the outward currents were activated by depolarizing step pulses and were outward rectified. It’s activation was very fast and the peak was reached within 10 msec. Inactivation time constant was between 600 msec and 1300 msec and tended to decrease at the higher depolarization. 40 mM TEA blocked the current about 80 % (79.76±2.06%, mean±S.E., n=9). The reactivation was voltage dependent and the repolarization to -80 mV fully recovered the channel activity. Reactivation time constant was 19.4 msec. The half maximal inactivation voltage was -26.4 mV and the slope factor was 7.0. The half maximal activation was 1.5 mV and the slope factor was 9.7. Changing the external K+ concentration shifted the reversal potential to the direction estimated by Nernst’s equation but the shifted amount was not matched the prediction by Nernst’s equation. The substitution of pipette K+ with Na+ or Cs+ also produced outward rectifying currents even though its amplitudes were smaller. This results was different from the previous report (Nenov et al., 1998). The inactivation time constant was changed and the most rapid one was recorded in K+ pipette conditions, the next was in Cs+ conditions and the slowest was in Na+ conditions. These results were suggested that external Na+ ions were passed through the outward rectifying K+ current and its physiological role needs to be further investigation.
Source: Korean Journal of Physiology & Pharmacology.2000 Oct;4(Suppl):S9-S9
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