Identification of ATP-sensitive potassium channel in frog ventricular myocytes.
ATP-sensitive potassium channels were found in frog ventricular myocytes using the inside-out patch-clamp technique. The channel was selectively permeable to K+. Single-channel conductance was 32.6 pS at 3.0 mM of [K+]o and 132 mM [K+]i and 77.3 pS at 114 mM [K+]o and 132 mM [K+]i. ATP did not affect single-channel conductance. The open probability of the channel was decreased by intracellular application of ATP in both the presence and absence of 2 mM MgCl2. The coexistence of Mg2+ with ATP shifts the dose-response curve for the open probability of ATP-sensitive K+ channel against ATP rightward. The shift of the curve indicates that Mg-ATP is less effective than free ATP in inhibiting the channel. An open-time histogram was fitted by a single exponential function with a time constant of 1.63 +/- 0.17 msec (n = 5) in an ATP-free medium. Mean open time (1.57 +/- 0.10 msec; n = 5) was not altered but the inter-burst time (closed time between bursts) lengthened in 10 microM ATP.
Munemori
M
M
Department of Physiology, School of Medicine, Hiroshima University, Kasumi 1-2-3, Minamiku, Hiroshima 734, Japan.
Yamaoka
K
K
Seyama
I
I
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000032:analysis* / Q000378:metabolism
D015221:Potassium Channels; D000255:Adenosine Triphosphate