Abstract
BL-1249 [(5,6,7,8-tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine] produced a concentration-dependent membrane hyperpolarization of cultured human bladder myocytes, assessed as either a reduction in fluorescence of the voltage-sensitive dye bis-(1,2-dibutylbarbituric acid)trimethine oxonol (EC50 = 1.26 ± 0.6 μM) or by direct electrophysiological measurement (EC50 = 1.49 ± 0.08 μM). BL-1249 also produced a membrane hyperpolarization of acutely dissociated rat bladder myocytes. Voltage-clamp studies in human bladder cells revealed that BL-1249 activated an instantaneous, noninactivating current that reversed near EK. The BL-1249-evoked outward K+ current was insensitive to blockade by glyburide, tetraethylammonium, iberiotoxin, 4-aminopyridine, apamin, or Mg2+. However, the current was inhibited by extracellular Ba2+ (10 mM). In in vitro organ bath experiments, BL-1249 produced a concentration-dependent relaxation of 30 mM KCl-induced contractions in rat bladder strips (EC50 = 1.12 ± 0.37 μM), yet had no effect on aortic strips up to the highest concentration tested (10 μM). The bladder relaxation produced by BL-1249 was partially blocked by Ba2+ (1 and 10 mM) but not by apamin, iberiotoxin, 4-aminopyridine, glyburide, or tetraethylammonium. In an anesthetized rat model, BL-1249 (1 mg/kg i.v.) decreased the number of isovolumic contractions, without significantly affecting blood pressure. Thus, BL-1249 behaves as a potassium channel activator that exhibits bladder versus vascular selectivity both in vitro and in vivo. A survey of potassium channels exhibiting sensitivity to extracellular Ba2+ at millimolar concentration revealed that the expression of the K2P2.1 (TREK-1) channel was relatively high in human bladder cells versus human aortic cells, suggesting this channel as a possible candidate target for BL-1249.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.078592.
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ABBREVIATIONS: KCO, potassium channel opener; MABP, mean arterial blood pressure; BL-1249, (5,6,7,8-tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine; DiBAC4(3), bis-(1,2-dibutylbarbituric acid)trimethine oxonol; PCR, polymerase chain reaction; RT, reverse transcriptase; PEG400, polyethylene glycol; ZD-6169, (S)-N-(4-benzoylphenyl)-3,3,3-trifluro-2-hydroxy-2-methyl-priopionamide; WAY-133537, (R)-4-[3,4-dioxo-2-(1,2,2,-trimethyl-propylamino)cyclobut-1-enylamino]-3-ethyl-benzonitrile.
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↵1 Current address: Abbott Laboratories, Global Pharmaceutical Research and Development, Abbott Park, IL.
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↵2 Current address: Vanderbilt Institute of Chemical Biology, Vanderbilt University Medical School, Nashville, TN.
- Received October 4, 2004.
- Accepted December 15, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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