TY - JOUR

T1 - Calmodulin antagonists suppress gap junction coupling in isolated Hensen cells of the guinea pig cochlea

AU - Blödow, Alexander

AU - Ngezahayo, Anaclet

AU - Ernst, Arne

AU - Kolb, Hans-Albert

PY - 2003/4

Y1 - 2003/4

N2 - The effect of calmodulin (CaM) antagonists W7, trifluoperazine (TFP) and a calmodulin inhibitory peptide on gap junction coupling in isolated Hensen cells of the organ of Corti was analysed by the double whole-cell patch-clamp technique. Addition of the conventional antagonists W7 and TFP in the micromolar range caused a rapid decrease of gap junction conductance after a delay of a few minutes in a dose-dependent manner. Fluorescence spectroscopy of cytoplasmic free calcium concentration ([Ca(2+)](i)) by Fura-2 showed no significant change of [Ca(2+)](i) by W7. Chelation of [Ca(2+)](i) by 10 mM BAPTA or use of nominally Ca(2+)-free external bath did not suppress the W7-induced gap junction uncoupling. The results suggest that W7 and TFP induce gap junction uncoupling at unchanged global [Ca(2+)](i) in Hensen cells. To obtain additional evidence for an involvement of CaM in regulating gap junction conductance a calmodulin inhibitory peptide, the MLCK peptide (250 nM), was added to the standard pipette solution. Again gap junction uncoupling was observed, but on a significantly slower time scale. This is the first study of an effect of calmodulin antagonists on gap junction coupling in isolated Hensen cells. The question whether the effect of calmodulin inhibitors is specific and involves CaM-dependent gating of gap junction coupling in Hensen cells is discussed.

AB - The effect of calmodulin (CaM) antagonists W7, trifluoperazine (TFP) and a calmodulin inhibitory peptide on gap junction coupling in isolated Hensen cells of the organ of Corti was analysed by the double whole-cell patch-clamp technique. Addition of the conventional antagonists W7 and TFP in the micromolar range caused a rapid decrease of gap junction conductance after a delay of a few minutes in a dose-dependent manner. Fluorescence spectroscopy of cytoplasmic free calcium concentration ([Ca(2+)](i)) by Fura-2 showed no significant change of [Ca(2+)](i) by W7. Chelation of [Ca(2+)](i) by 10 mM BAPTA or use of nominally Ca(2+)-free external bath did not suppress the W7-induced gap junction uncoupling. The results suggest that W7 and TFP induce gap junction uncoupling at unchanged global [Ca(2+)](i) in Hensen cells. To obtain additional evidence for an involvement of CaM in regulating gap junction conductance a calmodulin inhibitory peptide, the MLCK peptide (250 nM), was added to the standard pipette solution. Again gap junction uncoupling was observed, but on a significantly slower time scale. This is the first study of an effect of calmodulin antagonists on gap junction coupling in isolated Hensen cells. The question whether the effect of calmodulin inhibitors is specific and involves CaM-dependent gating of gap junction coupling in Hensen cells is discussed.

KW - Animals

KW - Calcium/metabolism

KW - Calcium-Calmodulin-Dependent Protein Kinases/antagonists & inhibitors

KW - Calmodulin/antagonists & inhibitors

KW - Cells, Cultured

KW - Electric Conductivity

KW - Gap Junctions/drug effects

KW - Guinea Pigs

KW - Membrane Potentials/physiology

KW - Organ of Corti/cytology

KW - Patch-Clamp Techniques

KW - Peptides/pharmacology

KW - Spectrometry, Fluorescence

KW - Sulfonamides/pharmacology

KW - Trifluoperazine/pharmacology

U2 - 10.1007/s00424-002-1004-9

DO - 10.1007/s00424-002-1004-9

M3 - Article

C2 - 12690460

VL - 446

SP - 36

EP - 41

JO - Pflugers Archiv European Journal of Physiology

JF - Pflugers Archiv European Journal of Physiology

SN - 0031-6768

IS - 1

ER -