Modulation of cell membrane potential in cultured vascular endothelium.
The present study explores the role of different ionic conductances in the regulation of membrane potential under resting conditions and after bradykinin (BK) or thapsigargin (TG) stimulation of cultured bovine aortic endothelial cells. Under resting conditions, the cell membrane potential observed was -62+/- 5 mV. The main conductance under these conditions is an inwardly rectifying potassium (IRK) channel. Application of 50 nM BK induced a transient hyperpolarization to -87 +/- 4 mV followed by sustained depolarization to -35 +/- 5 mV. The transient hyperpolarization was eliminated by 1 microM noxiustoxin, a blocker of calcium-activated postassium channels (K(Ca)). the sustained depolarization induced by BK was prevented by incubating the cells with the calcium channel blocker lanthanum. TG evoked a similar response in membrane potential, with the exception that the onset of the hyperpolarization was slower compared with BK. The results presented here indicate that the cell resting potential is maintained at -62 +/- 2 mV by the IRK channel. BK or TG stimulation induces a transient hyperpolarization of approximately -20 mV produced by activation of a KCa. This hyperpolarization is followed by a sustained depolarization produced by activation of a calcium-selective channel sensitive to lanthanum.
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Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
Licea
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Possani
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D000818:Animals; D001011:Aorta; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002417:Cattle; D002462:Cell Membrane / Q000502:physiology*; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D012604:Scorpion Venoms / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors
D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D012604:Scorpion Venoms; D013729:Terpenes; D004533:Egtazic Acid; D019284:Thapsigargin; D007811:Lanthanum; C052567:noxiustoxin; D000252:Calcium-Transporting ATPases; D001920:Bradykinin; D002118:Calcium