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Acquired long QT syndromes and torsade de points often occur with underlying hypokalemia andbradycardia. With its fast inactivation property, the rapid activating component (Ikr) of the delayed rectifierpotassium current (IK) plays an important role in maintaining normal QT intervals. In this study, we evaluated the effects of different extracellular potassium ([K].) on the fast inactivation current of Ikr in guinea pigventricular myocytes. The results showed that [K]. had strong effects on the fast inactivation current ; thelower [K].(1, 3 mmol/L) significantly decreased the inactivation outward current (P＜0. 05); while higher[K]. (8, 10, 20 mmol/L) slightly increased the inactivation current (P>0. 05). These results may be of greatclinical significance. The lower [K]. decreased Ikr inactivation current, which may help to explain why acquired long QT syndromes and torsade de points often occur in the lower [K]. The correction of hypokalemia can increase the inactivation current, therefore, it is critical in the treatment of acquired long QTsyndromes and torsade de points.
With its fast inactivation property, the rapid activating component (Ikr) of the delayed rectifier potassium (IK) plays an important role in maintaining normal QT intervals. In this study, we evaluated the effects of different extracellular potassium ([K].) on the fast inactivation current of Ikr in guinea pigventricular myocytes. The results showed that [K]. had strong effects on the fast inactivation current; thelower [K]. (3 mmol / L, 3 mmol / L) significantly decreased the inactivation current (P <0. 05); while higher [K] results may be of great clinical significance. The lower [K]. decreased Ikr inactivation current, which may help to explain why acquired long QT syndromes and torsade de points often occur in the lower [K]. The correction of hypokalemia can increase the inactivation current the refore, it is critical in the treatment of acquired long QTsyndromes and torsade de points.