Effects of Excess K+ on Carbachol-induced Contractions in the Guinea-Pig Tracheal Muscle.

• DOI: 10.1540/jsmr.34.45
• Publication Date: 2011-12-08T04:55:08Z
• Authors: Masanori TAKEMOTO; Yasushi ITO; Kenzo TAKAGI; Kayo OGINO; Tadao TOMITA
• Keywords: Cyclopiazonic acid; ED50; Thapsigargin

1. In smooth muscles isolated from the guinea-pig trachea, effects of dihydropyridines, nifedipine and nicardipine on contractions produced by carbachol (Cch) were studied in normal (6 mM) excess K+ concentration (60 mM). The tonic contraction 1 microM Cch was highly dependent external Ca2+ ([Ca2+]0) not significantly affected cyclopiazonic acid or thapsigargin, uptake inhibitor. 2. [Ca2+]0-tension curves steeper presence (the Hill coefficient: 2.5) than 60 mM (Hill 1.6) their ED50 0.16 0.39 mM, respectively. An increase to shifted curve left roughly parallel (ED50: 0.12 2.3). 3. right (1 microM). This markedly potentiated being 3 times at 6 15 K+). No tension evoked up 2.5 solution containing but no Cch. 4. absence nifedipine, Cch-induced K+, whereas inhibited K+. These mechanical changes accompanied an a decrease intracellular Ca2+. 5. A hypothesis is presented explain results which suggests that kinetics influx though single type pathway modulated membrane potential receptor activation susceptibility dihydropyridine blockade closely related with reducing depolarization increasing susceptibility.