Characterization of a newly found stretch-activated KCa,ATP channel in cultured chick ventricular myocytes

Am J Physiol. 1999 Jun;276(6):H1827-38. doi: 10.1152/ajpheart.1999.276.6.H1827.

Abstract

With the use of the patch-clamp technique, five kinds of stretch-activated (SA) ion channels were identified on the basis of their single-channel conductances and ion selectivities in cultured chick ventricular myocytes. Because a high-conductance K+-selective channel predominated among these channels, we concentrated on characterizing its properties mostly using excised inside-out patches. With 145 mM KCl solution in the pipette and the bath, the channel had a conductance of 199.8 +/- 8.2 pS (n = 22). The ion selectivities among K+, Na+, Ca2+, and Cl- as estimated from their permeability ratios were PNa/PK = 0.03, PCa/PK = 0.025, and PCl/PK = 0.026. The probability of the channel being open (Po) increased with the Ca2+ concentration in the bath ([Ca2+]b; dissociation constant Kd = 0.51 microM at +30 mV) and membrane potential (voltage at half-maximal Po = 39.4 mV at 0.35 microM [Ca2+]b). The channel was blocked by gadolinium, tetraethylammonium, and charybdotoxin from the extracellular surface and, consequently, was identified as a Ca2+-activated K+ (KCa) channel type. The channel was also reversibly activated by ATP applied to the intracellular surface (Kd = 0.74 mM at 0.10 microM [Ca2+]b at +30 mV). From these data taken together, we concluded that the channel is a new type of KCa channel that could be designated as an "SA KCa,ATP channel." To our knowledge, this is the first report of KCa channel in heart cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine Nucleotides / pharmacology
  • Adenosine Triphosphate / physiology*
  • Animals
  • Calcium / physiology*
  • Cells, Cultured
  • Chick Embryo
  • Electric Conductivity
  • Electrophysiology
  • Heart Ventricles
  • Ions
  • Kinetics
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Physical Stimulation
  • Potassium Channel Blockers
  • Potassium Channels / metabolism*
  • Potassium Channels / physiology
  • Pressure

Substances

  • Adenine Nucleotides
  • Ions
  • Potassium Channel Blockers
  • Potassium Channels
  • Adenosine Triphosphate
  • Calcium