ATP-dependent activation of atrial muscarinic K+ channels in the absence of agonist and G-nucleotides

Pflugers Arch. 1990 Apr;416(1-2):213-5. doi: 10.1007/BF00370246.


While opening of cardiac muscarinic K+ channels is mediated by a guanine nucleotide-binding protein, GK, and normally requires both ACh and cytosolic GTP, we demonstrate that in the absence of agonist and G-nucleotides guinea-pig atrial muscarinic K+ channels are activated by cytosolic ATP (K50 = 224 microM). This activation involves a phosphorylating reaction and is most probably related to a transphosphorylation by a nucleoside diphosphate kinase (NDPK) from ATP to GK-bound GDP. This ATP-induced response is completely inhibited by nanomolar concentrations of GDP or GTP, suggesting a G-nucleotide specific binding site on NDPK.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Adenosine Triphosphate / metabolism*
  • Adenosine Triphosphate / pharmacology
  • Animals
  • GTP-Binding Proteins / metabolism*
  • Guanosine Diphosphate / pharmacology
  • Guanosine Triphosphate / pharmacology
  • Guinea Pigs
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Phosphorylation
  • Potassium Channels / metabolism*
  • Receptors, Muscarinic / metabolism*


  • Potassium Channels
  • Receptors, Muscarinic
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • Adenosine Triphosphate
  • GTP-Binding Proteins
  • Acetylcholine