Effects of Excess K^+ on Carbachol-induced Contractions in the Guinea-Pig Trancheal Muscle

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概要

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• 1.In smooth muscles isolated from the guinea-pig trachea, the effects of dihydropyridines, nifedipine and nicardipine on contractions produced by carbachol(Cch)were studied in normal(6 mM)and excess K^+ concentration(60 mM). The tonic contraction produced by 1 μM Cch was highly dependent on the external Ca^<2+> concentration([Ca^<2+>]_0)and was not significantly affected by cyclopiazonic acid or thapsigargin, Ca^<2+> uptake inhibitor. 2.[Ca^<2+>]_0-tension curves were steeper in the presence of 1 μM Cch(the Hill coefficient:2.5)than in the presence of 60 mM K^+(Hill coefficient:1.6)and their ED_<50> of Ca^<2+> was 0.16 and 0.39 mM, respectively. An increase of K^+ to 60 mM in the presence of 1μM Cch shifted the curve to the left roughly in parallel(ED_<50>:0.12 mM, Hill coefficient:2.3). 3.[Ca^<2+>]_0-tension curve in the presence of 1 μM Cch was shifted to the right in parallel by nifedipine(1 μM). This was markedly potentiated by 60 mM K^+(the increase in ED_<50> of Ca^<2+> being 3 times at 6 mM and 15 times at 60 mM K^+). No tension was evoked by Ca^<2+> up to 2.5 mM in 60 mM K^+ solution containing 1 μM nifedipine but no Cch. 4.In the absence of nifedipine, Cch-induced contractions were potentiated by 60 mM K^+, whereas in the presence of nifedipine, Cch-induced contractions were markedly inhibited by 60 mM K^+. These mechanical changes were accompanied by an increase or a decrease in intracellular Ca^<2+>. 5.A hypothesis is presented to explain the results which suggests that the kinetics of Ca^<2+> influx though a single type of pathway is modulated by membrane potential and receptor activation and that the susceptibility of the pathway to dihydropyridine blockade is closely related to the Ca^<2+> influx kinetics with receptor activation reducing and membrane depolarization increasing the susceptibility.

• 日本平滑筋学会の論文

著者

• Tomita T

  Institute For Comprehensive Medical Science Fujita Health University

• Tomita Tadao

  Institute For Comprehensive Medical Science Fujita Health University

• Takagi Kenzo

  The Second Department Of Internal Medicine School Of Medicine Nagoya University

• OGINO Kayo

  Institute for Comprehensive Medical Science, Fujita Health University

• TAKEMOTO Masanori

  The Second Department of Internal Medicine, School of Medicine, Nagoya University

• ITO Yasushi

  The Second Department of Internal Medicine, School of Medicine, Nagoya University

• Ogino Kayo

  藤田保健衛生大学総合医科学研究所

• Ogino Kayo

  Institute For Comprehensive Medical Science Fujita Health University

• Takemoto Masanori

  The Second Department Of Internal Medicine School Of Medicine Nagoya University

• Ito Yasushi

  The Second Department Of Internal Medicine School Of Medicine Nagoya University

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• Effects of Removal and Reapplication of K^+ and Cl^- on Spontaneous Electrical Activity, Slow Wave, in the Circular Muscle of the Guinea-Pig Gastric Antrum
• Effects of Excess K^+ on Carbachol-induced Contractions in the Guinea-Pig Trancheal Muscle
• Effects of Removal of Na^+ and Cl^- on Spontaneous Electrical Activity, Slow Wave, in the Circular Muscle of the Guinea-Pig Gastric Antrum
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