Components of depolarization-induced transmembrane ion current in isolated smooth muscle cells of the guinea pigtaenia coli |
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Authors: | A V Povstyan A V Zima V L Reznikov Ya D Tsytsyura M F Shuba |
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Institution: | (1) Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine |
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Abstract: | Transmembrane ion currents in isolated single smooth muscle cells (SMC) from the guinea pigtaenia coli were investigated using a whole-cell mode of the patch-clamp technique. Currents induced by depolarizing shifts in the membrane
potential from its holding level of −60 mV contained an initial inward phase (Ca2+ current), which in 30–40 msec was followed by an outward phase. It was shown that outward current was carried by K ions and
consisted at least of three components: one Ca2+-independent K+ current of delayed rectifier (KV) and two Ca2+-dependent K+ currents. The latter can be further divided into the apamin-sensitive (SK) and charybdotoxin-sensitive (BK) currents. It
was found that relative contributions of these three components in total outward current at 0 mV were 35–45%, 5–15%, and 45–55%
for KV, SK, and BK currents, respectively. A potential-dependent current carried by Ci ions was also found. This Cl− current had inward direction within the range of potentials below the chloride equilibrium potential (E
Cl) and outward direction above theE
Cl. The magnitude of Cl− current was significantly lower than the magnitude of total K+ current. |
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