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KMID : 0811720070110050207
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Korean Journal of Physiology & Pharmacology
2007 Volume.11 No. 5 p.207 ~ p.213
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Regulation of Ba2+-Induced Contraction of Murine Ureteral Smooth Muscle
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Kim Young-Chul
Kim Wun-Jae
Myung Soon-Chul
Lee Sang-Jin
Kim Seung-Ryul
Xu Wen-Xie
Kim Chan-Hyung
Lee Moo-Yeol
Choi Woong
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Abstract
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This study was designed to characterize ureteral smooth muscle motility and also to study the effect of forskolin (FSK) and isoproterenol (ISO) on smooth muscle contractility in murine ureter. High K+ (50 mM) produced tonic contraction by 0.17±0.06 mN (n=19). Neuropeptide and neurotransmitters such as serotonin (5μM), histamine (20μM), and carbarchol (CCh, 10∼50μM) did not produce significant contraction. However, CCh (50μM) produced slow phasic contraction in the presence of 25 mM K+. Cyclopiazonic acid (CPA, 10μM), SR Ca2+-ATPase blocker, produced tonic contraction (0.07 mN). Meanwhile, inhibition of mitochondria by protonophore carbnylcyanide m-chlorophenylhydrazone (CCCP) also produced weak tonic contraction (0.01 mN). The possible involvement of K+ channels was also pursued. Tetraethyl ammonium chloride (TEA, 10 mM), glibenclamide (10μM) and quinidine (20 μM) which are known to block Ca2+-activated K+ channels (KCa channel), ATP-sensitive K+ channels (KATP) and nonselective K+ channel, respectively, did not elicit any significant effect. However, Ba2+ (1∼2 mM), blocker of inward rectifier K+ channels (KIR channel), produced phasic contraction in a reversible manner, which was blocked by 1μM nicardipine, a blocker of dehydropyridine-sensitive voltage-dependent L-type Ca2+ channels (VDCCL) in smooth muscle membrane. This Ba2+-induced phasic contraction was significantly enhanced by 10μM cyclopiazonic acid (CPA) in the frequency and amplitude. Finally, regulation of Ba2+-induced contraction was studied by FSK and ISO which are known as adenylyl cyclase activator and β-adrenergic receptor agonist, respectively. These drugs significantly suppressed the frequency and amplitude of Ba2+-induced contraction (p＜0.05). These results suggest that Ba2+ produces phasic contraction in murine ureteral smooth muscle which can be regulated by FSK and β-adrenergic stimulation.
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KEYWORD
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Ureter, Murine smooth muscle, Ba2+, Isoproterenol (ISO), Cyclopiazonic acid (CPA)
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