[Outwardly rectifying potassium currents in isolated outer hair cells in cochlea of guinea pig].

OBJECTIVE

The purpose of this study was to investigate electrophysiological properties of isolated outer hair cells (OHCs) from cochlea of the guinea pig, record outwardly rectifying potassium currents in OHCs with different length, analyze component of outwardly rectifying potassium currents, study kinetics of the currents.

METHOD

The whole cell patch-clamp technique was used.

RESULT

Whole-cell capacitance of the OHC was (30.96 +/- 2.79) pF(n = 29), zero current potential was (30 +/- 2.1) mV(n = 16) and reversal potential was (-51.67 +/- 1.84) mV(n = 9). Variation in expression of outwardly rectifying potassium currents was found in OHCs with different length, namely, potassium conductance was greater in short OHC than in tall OHC. The maximal amplitude of outwardly rectifying potassium currents were reduced by 60% in the presence of 100 mumol/L CdCl2 and change the kinetics of the currents, effects of CdCl2 on the peak currents were greater when compared to the effects on the steady-state currents (P < 0.01, n = 5). 1 mmol/L 4-aminopyridine (4-AP) inhibited 43% of the maximal amplitude of the currents and had no effect on the kinetics of the currents. Activation of the currents was described by Boltzmann equation, V1/2 = (-11.07 +/- 0.26) mV, S = (6.62 +/- 1.74) mV(n = 13).

CONCLUSION

Outwardly rectifying potassium currents were composed of calcium-activated potassium current, outward delayed rectifier potassium current and A type current.