title: Properties of the LP-805-induced potassium currents in cultured bovine pulmonary artery endothelial cells.
abstract: The actions of 8-tert-butyl-6,7-dihydropyrolo[3,2-e]-5- methylpyrazolo[1,5-a]pyrimidine-3-carbonitrile (LP-805) on membrane K+ currents in cultured bovine pulmonary artery endothelial cells were investigated using the patch-clamp technique. In the whole-cell voltage clamp experiments, with 11 mM ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) in the pipette, membrane currents revealed only an inwardly rectifying K+ current, and no outward current could be observed at depolarized potentials. Using a pipette solution containing 0.3 mM EGTA, outward K+ current was present in response to depolarizing voltage steps from a holding potential of -60 mV. LP-805 (1-10 microM) significantly increased outward K+ currents in a concentration-dependent manner. The increase of this K+ current was inhibited by 5 mM tetraethylammonium and 5 mM tetrabutylammonium to a level less than the control. Partial recovery occurred on washout. However, the increase of outward K+ current by 10 microM LP-805 was unaffected by 5 mM 4-aminopyridine and 1 microM glibenclamide. LP-805 (1-10 microM) significantly decreased the inwardly rectifying K+ current in a concentration-dependent manner. In cell-attached patches, inward single K+ currents were recorded at negative membrane potentials, and single channel conductance was 23 +/- 2 pS (n = 5). No outward current could be observed at positive potentials. LP-805 (10 microM) inhibited the inwardly rectifying K+ currents. Thus LP-805 inhibits inwardly rectifying K+ currents but activates outward Ca(++)-dependent K+ currents in bovine pulmonary artery endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Inazu
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: E E
authors.initials: EE
authors.lastname: Daniel
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects*; D011651:Pulmonary Artery; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D015221:Potassium Channels; D011720:Pyrazoles; D011743:Pyrimidines; D000644:Quaternary Ammonium Compounds; D013757:Tetraethylammonium Compounds; D014665:Vasodilator Agents; C073993:8-tert-butyl-6,7-dihydropyrrolo(3,2-e)-5-methylpyrazolo(1,5-a)pyrimidine-3-carbonitrile; D019789:Tetraethylammonium; D015761:4-Aminopyridine; C009405:tetrabutylammonium; D005905:Glyburide