Calcium-dependent inactivation of the ATP-sensitive K+ channel of rat ventricular myocytes.
Single-channel currents were recorded from ATP-sensitive K+ channels in inside-out membrane patches excised from isolated rat ventricular myocytes. Perfusion of the internal surface of excised membrane patches with solutions which contained between 5 and 100 microM free calcium caused the loss of K+ATP channel activity which was not reversed when the membranes were washed with Ca-free solution. K+ATP channel activity could be recovered by bathing the patches in Mg.ATP. The loss of K+ATP channel activity provoked by internal calcium was a process which occurred over a time scale of seconds. Channel closure evoked by internal ATP was essentially instantaneous. The speed of K+ATP channel inactivation increased with the concentration of calcium. Neither a phosphatase inhibitor (fluoride ions) nor a proteinase inhibitor (leupeptin) had any effect upon the loss of K+ channel activity stimulated by internal calcium.
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Laboratoire de Physiologie Comparée, (UA CNRS 1121), Université de Paris XI, Orsay, France.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity; D005459:Fluorides / Q000494:pharmacology; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats
D007473:Ion Channels; D007976:Leupeptins; D000255:Adenosine Triphosphate; C032854:leupeptin; D005459:Fluorides; D011188:Potassium; D002118:Calcium