Stretch-activated single ion channel currents in tissue-cultured embryonic chick skeletal muscle

J Physiol. 1984 Jul;352:685-701. doi: 10.1113/jphysiol.1984.sp015317.

Abstract

The membrane of tissue-cultured chick pectoral muscle contains an ionic channel which is activated by membrane stretch. Nicotinic channels and Ca2+-activated K+ channels are not affected by stretch. In 150 mM-external K+ and 150 mM-internal Na+ the channel has a conductance of 70 pS, linear current-voltage relationship between -50 and -140 mV and a reversal potential of +30 mV. Kinetic analysis of single-channel records indicates that there are one open (O) and three closed (C) states. The data can be fitted by the reaction scheme: C1-C2-C3-O. Only the rate constant that governs the C1-C2 transition (k1,2) is stretch-sensitive. None of the rates are voltage-sensitive. The rate constant k1,2 varies with the square of the tension as k1, 2 = k0 X e alpha T2, where alpha is a constant describing the sensitivity to stretch and T is the tension. A typical value of alpha is 0.08 (dyn cm-1)-2. Following exposure to cytochalasin B the channel becomes more sensitive to stretch. The stretch-sensitivity constant, alpha, increases from 0.08 to 2.4 (dyn cm-1)-2. The probability of the channel being open is strongly dependent upon the extracellular K+ concentration. With a suction of 2 cmHg the probability increases from 0.004 in normal saline (5 mM-K+) to 0.26 in 150 mM-K+. The channel appears to gather force from a large area of membrane (greater than 3 X 10(5) A2), probably by a cytochalasin-resistant cytoskeletal network.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials
  • Animals
  • Calcium / pharmacology
  • Cell Membrane / physiology
  • Cells, Cultured
  • Chick Embryo
  • Cytochalasins / pharmacology
  • Electric Conductivity
  • Ion Channels / physiology*
  • Kinetics
  • Mechanoreceptors / physiology
  • Models, Biological
  • Muscles / embryology
  • Muscles / physiology*
  • Potassium / physiology
  • Time Factors

Substances

  • Cytochalasins
  • Ion Channels
  • Potassium
  • Calcium