Abstract
High-conductance Ca2+-activated K+ (BKCa) channels from isolated adult guinea-pig outer hair cells were studied in inside-out membrane patches. They had a 300 pS unitary conductance and were inhibited by tetraethyl ammonium (1 mM), iberiotoxin (33 nM) and charybdotoxin (50 nM). In symmetrical 144 mM KCl their K+ permeability (PK) was 5.4×10−13 cm3/s; this was reduced to around 4.5×10−13 cm3/s with 160 mM Na+ in place of K+ on either internal or external membrane surface. BKCa channels from trypsin-isolated hair cells
had a high open probability, that depended on both membrane voltage (16
mV/e-fold change) and the concentration of calcium ions at their
intracellular surface ([Ca2+]i). The Hill coefficient was 3–4. About 50% of BKCa
channels from mechanically isolated outer hair cells had similar
characteristics; the remainder had the same high conductance but a low
open probability. Trypsin (<0.5 mg/ml) applied to the intracellular
face of these ‘inactive’ channels markedly increased their open
probability. It is possible that exposure to trypsin during cell
isolation removes an inactivating β subunit. This would account for the
absence of ‘inactive’ BKCa channels in trypsin-isolated cells.
Translated title of the contribution | Effects of trypsin on large-conductance Ca2+-activated K+ channels of guinea-pig outer hair cells |
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Original language | English |
Pages (from-to) | 115-127 |
Number of pages | 13 |
Journal | Hearing Research |
Volume | 190 |
Issue number | 1-2 |
Early online date | 2 Mar 2004 |
DOIs | |
Publication status | Published - Apr 2004 |
Keywords
- Ca2+-activated K+ channel
- Cochlea
- Outer hair cell