An ATP-sensitive potassium conductance in rabbit arterial endothelial cells.
1. Whole-cell patch clamp recording was used to study an ATP-sensitive, sulphonylurea-inhibitable potassium (K+) conductance in freshly dissociated endothelial cells from rabbit arteries. 2. The ATP-sensitive K+ conductance was activated by micromolar concentrations of the K+ channel opener, levcromakalim, and by metabolic inhibition of endothelial cells using dinitrophenol and iodoacetic acid. The current-voltage (I-V) relationship obtained in isotonic K+ solutions was linear between -150 and -50 mV and had a slope conductance of approximately 1 nS. 3. The permeability of the ATP-sensitive K+ conductance determined from reversal potential measurements exhibited the following ionic selectivity sequence: Rb+ > K+ > Cs+ >> Na+ > NH4+ > Li+. 4. Membrane currents activated by either levcromakalim or metabolic inhibition were inhibited by the sulphonylurea drugs, glibenclamide and tolbutamide, with half-maximal inhibitory concentrations of 43 nM and 224 microM and Hill coefficients of 1.1 and 1.2, respectively. Levcromakalim-induced currents were also inhibited by millimolar concentrations of Ba2+ or tetraethylammonium ions in the external solution. 5. Levcromakalim (3 microM) and metabolic inhibition hyperpolarized endothelial cells by approximately 10-15 mV in normal physiological salt solutions. The hyperpolarization induced by levcromakalim or metabolic inhibition was inhibited by bath application of 10 microM glibenclamide. 6. Internal perfusion of the cytosol of whole-cell voltage-clamped endothelial cells with an ATP-free pipette solution activated a membrane current which was reversibly inhibited by internal perfusion with a 3 mM MgATP pipette solution. This current was insensitive to other adenine and guanine nucleotides in the pipette solution. The inward current evoked in a nominally ATP-free internal solution was further increased by bath application of levcromakalim. 7. Levcromakalim (25 microM) did not induce a change in the intracellular Ca2+ concentration of fura-2-loaded endothelial cells, whereas metabolic inhibition caused a slow and sustained increase in intracellular Ca2+ concentration, which was attenuated by 10 microM glibenclamide applied externally.(ABSTRACT TRUNCATED AT 400 WORDS)
Katnik
C
C
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, FL 33101, USA.
Adams
D J
DJ
D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001011:Aorta; D001578:Benzopyrans / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D019806:Cromakalim; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D011651:Pulmonary Artery; D011758:Pyrroles / Q000494:pharmacology*; D011817:Rabbits; D013453:Sulfonylurea Compounds / Q000494:pharmacology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D001578:Benzopyrans; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011758:Pyrroles; D013453:Sulfonylurea Compounds; D013757:Tetraethylammonium Compounds; D014665:Vasodilator Agents; D019806:Cromakalim; D019789:Tetraethylammonium; D000251:Adenosine Triphosphatases; D002118:Calcium