Effect of Ca2+ ionophores on membrane potential of pig coronary artery endothelial cells.
Ca2+ ionophores (A23187 and ionomycin) were used to determine whether an increase in cytosolic Ca2+ plays a direct role in pig coronary endothelial cell hyperpolarization. Ionophores induced concentration-dependent hyperpolarizations that were not altered by the presence of N omega-nitro-L-argnine (L-NNA), and inhibitor of nitric oxide synthesis. d-Tubocurarine decreased by 65-89% the A23187- and substance P (SP)-generated hyperpolarization of endothelial cells. To study the role of endothelial cell hyperpolarization in the endothelium-dependent relaxation of precontracted coronary artery strips, A23187 and SP concentration-response curves were built up in the presence of d-tubocurarine and/or L-NNA. A decrease in the maximal response was observed only when both d-tubocurarine and L-NNA were present. Our direct in situ approach gives results in agreement with a gating of Ca(2+)-activated K+ channels during A23187- and SP-induced hyperpolarizations of endothelial cells. We suggest that these hyperpolarizations play a role in the endothelial cell-dependent relaxation induced by A23187 and SP in the pig coronary artery.
von der Weid
P Y
PY
Department of Zoology and Animal Biology, University of Geneva, Switzerland.
Bény
J L
JL
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology*; D016764:Cell Polarity; D003331:Coronary Vessels / Q000187:drug effects; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D019335:Nitroarginine; D015221:Potassium Channels / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology; D013552:Swine; D014403:Tubocurarine / Q000494:pharmacology; D014664:Vasodilation
D015221:Potassium Channels; D019335:Nitroarginine; D013373:Substance P; D000001:Calcimycin; D015759:Ionomycin; D001120:Arginine; D014403:Tubocurarine