Neuromodulation of calcium current by extracellular ATP in isolated ventricular myocytes.
The effects of extracellular ATP on the L-tpe Ca2+ current (ICa), action potential, and resting and intracellular Ca2+ levels were examined in enzymatically isolated myocytes from the right ventricles of ferrets. Extracellular ATP decreased the peak amplitude of ICa in a time- and concentration-dependent manner. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, it did decrease the Ca2+ transient. The effects of extracellular ATP were mediated independently of adenosine A1 receptors and a pertussis-toxin sensitive G protein. Pharmacological characterization of receptor subtype using ATP analogs was consistent with ATP binding to a P2Y type receptor.
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Department of Medicine, Duke University Med. Center, Durham, NC 27710.
Campbell
D L
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Himmel
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Strauss
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HC
D000200:Action Potentials / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005289:Ferrets; D019204:GTP-Binding Proteins / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D018377:Neurotransmitter Agents / Q000502:physiology*; D037342:Pertussis Toxin; D015398:Signal Transduction / Q000187:drug effects; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018377:Neurotransmitter Agents; D010566:Virulence Factors, Bordetella; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium