Abstract
It is unclear whether chromanol 293B, a selective inhibitor of slow component of delayed rectifier K + current ( I Ks), may affect other K + currents in human atrium. With whole-cell patch configuration, we evaluated effects of 293B on transient outward K + current ( I to1) and ultra-rapid delayed rectifier K + current ( I Kur) in isolated human atrial myocytes. It was found that 293B inhibited I to1 and I Kur in a concentration-dependent manner. At 10 μM 293B suppressed I to1 to 3.4 ± 0.4 from 5.1 ± 0.3 pA/pF ( P < 0.01), and I Kur to 1.5 ± 0.2 from 2.1 ± 0.3 pA/pF ( P < 0.01) at +50 mV. The inhibition of I to1 and I Kur was independent of depolarizing voltage, and the concentration of 50% inhibition was 31.2 μM for I to1, and 30.9 μM for I Kur. 293B blocked I to1 and I Kur with the same concentration range, and the significant effect was observed from the concentration of 1 μM. The maximum inhibitive effect was 88% for I to1 and 96% for I Kur at 250 μM. Voltage dependence of activation and inactivation, and time-dependent recovery from inactivation of I to1 were not altered by 293B; however, time to peak and time-dependent inactivation of I to1 was significantly accelerated. The results indicate that 293B significantly inhibits the major repolarization K + currents I to1 and I Kur in human atrial myocytes.
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