To identify the presence of inwardly rectifying K+ channels and its characteristics, membrane currents were measured using a whole-cell patch clamp from isolated gastric myocytes of guinea-pig. Change of external K+ concentration from 5 to 90 mM induced an inward current at a holding potential of -80 mV. The high K+-induced inward current was blocked by Ba2+ and Cs+, but not by glibenclamide. With 90 mM K+ in bath, the Ba2+- and Cs+-sensitive currents showed strong inward rectification. Ten mM TEA weakly blocked the inward current only at potentials more negative than -50 mV. With 90 mM K+ in bath, hyperpolarizing step pulses from -10 mV induced inward currents, which were inactivated at potentials more negative than -70 mV. Reduction of external K+ to 60 mM decreased the amplitudes of the currents and shifted the reversal potential to more negative potential. The inactivation of inward K+ current at negative clamp voltage was not affected by removing external Na+. These results suggest that the inwardly rectifying K+ channels may exist in gastric smooth muscle.
|Number of pages||9|
|Journal||Korean Journal of Physiology and Pharmacology|
|Publication status||Published - 2002 Jan 1|
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