Low-conductance states of K+ channels in adult mouse skeletal muscle.
Single-channel currents were recorded from Ca2+-activated or ATP-sensitive K+ channels in inside-out membrane patches excised from isolated mouse toe muscles. In addition to the closed and fully open configurations, both types of channels may exhibit several intermediate low-conductance states which are clustered near multiples of elementary conductance units. The units are 1/8 or 1/6 of the channel conductance for Ca2+-activated channels and 1/4 or 1/3 for ATP-sensitive channels. Normally, low-conductance states are rare, but they occur more frequently directly after patch excision. An increased probability of low-conductance states of ATP-sensitive K+ channels was also observed in the presence and during washout of the internal channel blocker adenine. The results suggest that Ca2+-activated and ATP-sensitive K+ channels are composed of several membrane pores with strong positive cooperativity among the elementary conductance units.
I. Physiologisches Institut, Universität des Saarlandes, Homburg, F.R.G.
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R
Weik
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U
Lönnendonker
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B
Neumcke
D000255:Adenosine Triphosphate / Q000502:physiology; D000375:Aging / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology; D004553:Electric Conductivity; D051379:Mice; D009132:Muscles / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels; D000255:Adenosine Triphosphate; D002118:Calcium