Coupling of a P2Z-like purinoceptor to a fatty acid-activated K(+) channel in toad gastric smooth muscle cells

J Physiol. 2001 Jul 1;534(Pt 1):59-70. doi: 10.1111/j.1469-7793.2001.00059.x.

Abstract

1. Extracellular application of ATP generates two whole-cell currents in toad gastric smooth muscle cells: an immediate inward non-selective cation current (due to the activation of a P2X or P2Z-like receptor) and a slowly developing outward K(+) current. The inward non-selective cation current depends on the continuous presence of ATP while the outward K(+) current can last for minutes after ATP application ceases. 2. In cell-attached patches, application of ATP to the extra-patch membrane can activate K(+) channels in the patch indicating that a diffusible cellular messenger may be involved. The characteristics of these K(+) channels are similar to those of a previously described fatty acid-activated K(+) channel that is also a stretch-activated channel. 3. This whole-cell K(+) current can be induced by ATP in the absence of extracellular Ca(2+) (with EGTA present to chelate trace amounts). However, the current generated in the presence of extracellular Ca(2+) is considerably larger. 4. The pharmacological profiles for the activation of the non-selective cation current and the K(+) current are similar, suggesting that the same P2Z-like receptor could be mediating both responses. This type of plasma membrane receptor/channel-channel coupling by a process that does not appear to involve Ca(2+) flow through the receptor/channel or a subsequent membrane potential change may be representative of a new class of signalling mechanisms.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / physiology
  • Animals
  • Bufo marinus
  • Calcium / metabolism
  • Cell Membrane / physiology
  • Electric Conductivity
  • Electrophysiology
  • Extracellular Space / metabolism
  • Fatty Acids / physiology*
  • GTP-Binding Proteins / physiology
  • Gastric Mucosa / metabolism*
  • Intracellular Fluid / metabolism
  • Muscle, Smooth / cytology
  • Muscle, Smooth / metabolism*
  • Osmolar Concentration
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism*
  • Receptors, Purinergic P2 / metabolism*
  • Receptors, Purinergic P2X7
  • Stomach / cytology

Substances

  • Fatty Acids
  • Potassium Channels
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X7
  • Adenosine Triphosphate
  • GTP-Binding Proteins
  • Calcium