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Activation of Ca 2+ ‐activated K + channels by an increase in intracellular Ca 2+ induced by depolarization of mouse skeletal muscle fibres
Author(s) -
Jacquemond Vincent,
Allard Bruno
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.093bo.x
Subject(s) - depolarization , pipette , conductance , biophysics , chemistry , reversal potential , intracellular , patch clamp , repolarization , membrane potential , electrophysiology , analytical chemistry (journal) , biochemistry , physics , neuroscience , biology , chromatography , receptor , condensed matter physics
1 Ionic currents were simultaneously recorded at macroscopic and unitary level using the whole‐cell and cell‐attached patch‐clamp procedures together on the same portion of isolated mouse skeletal muscle fibres. 2 In the presence of Tyrode solution in the patch pipette and Tyrode‐TTX solution in the bath, macroscopic and unitary currents through delayed rectifier K + channels were simultaneously recorded in response to depolarizing pulses of 1 s duration. 3 In five fibres, successive long‐lasting incremental depolarizing levels induced, at ‐40 mV or ‐30 mV, the opening of a high conductance channel carrying an outward current superimposed on delayed rectifier K + channel activity. Opening of this high conductance channel was not observed when the depolarization steps were applied in the patch pipette. 4 Using the same depolarizing protocol, activation of a high conductance channel was also observed in two fibres in the presence of a K + ‐rich solution in the pipette (145 m m K + ). 5 With either Tyrode or K + ‐rich solution in the pipette, unitary current amplitudes of the high conductance channel matched well with the values obtained for Ca 2+ ‐activated K + (K Ca ) channels in inside‐out patches under similar ionic conditions. 6 Indo‐1 fluorescence measurements showed that the stimulation protocol that led to K Ca channel opening induced stepwise increases in intracellular [Ca 2+ ] in the submicromolar range. 7 Our results provide evidence that activation of sarcolemmal K Ca channels can be induced by a rise in intracellular [Ca 2+ ] following voltage‐activated sarcoplasmic reticulum Ca 2+ release.