Lead (Pb2+) modulation of potassium currents of guinea pig outer hair cells.
Outer hair cells (OHC) are mechanosensitive sensory cells of the inner ear cochlea and are involved in modulating the activity of inner hair cells in the transduction of an acoustic stimulus. Potassium (K(+)) currents play an important role in the sensory transduction process. K(+) currents were recorded from acutely dissociated OHC obtained from the guinea pig organ of Corti. The whole-cell patch clamp technique was employed. We identified a channel that exhibited outward current of the delayed rectifier type (Kv). Kv channels mediating inward currents carried by potassium ions were also identified and took on the appearance of a previously described inwardly rectifying current. Lead (Pb(2+)) acetate at concentrations of 0.1, 1.0, 10, and 100 microM was bath applied. Time to activation for outward-going current was not affected by Pb(2+). The time course of Pb(2+) effects was seen as a dose-dependent reduction of K(+) current over time, with very little or no recovery after washout. Pb(2+) inhibited the outward Kv relative current with values of 0.10, 0.14, 0.18, and 0.30 at 0.1, 1.0, 10, and 100 microM, respectively. Pb(2+) did not modulate time to activation, peak current, or inactivation of inward I(K). The effects of Pb(2+) on the potassium currents of OHC are not remarkable and therefore OHC are probably not a major cause of purported peripheral hearing loss observed in Pb(2+)-exposed animals and humans.
Liang
G-H
GH
Center for Hearing and Communication Research, Department of Clinical Neuroscience, Karolinska Institutet, S-171 76 Stockholm, Sweden.
Järlebark
L
L
Ulfendahl
M
M
Bian
J-T
JT
Moore
E J
EJ
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects*; D007854:Lead / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques / Q000379:methods; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D015221:Potassium Channels; D007854:Lead; D011188:Potassium