CHARACTERISTICS OF TRANSIENT OUTWARD K+ CURRENT IN HUMAN ATRIAL CARDIOMYOCYTES

AIM: To study the properties of transient outward potassium current (I -to) in human atrial myocytes. METHODS: The patch-clamp whole-cell rec ording techniques were used. When the calcium inward current was block ed by CdCl2(0.1 mmol . L-1), the transient outward potassium current ( I-to) was recorded by depolarizing cells. RESULTS: The current was vol tage dependent, it was activated quickly and inactivated rapidly too. 4-Aminopyridine (4-AP) 10 mmol . L-1 (a selective blocker of I-to)bloc ked the current completely. The IC50 (95 % confidence limits) of 4-AP on I-to were 0.67 (0.58 - 0.80) mmol . L-1, 4-AP 1 mmol . L-1 shifted the activation curve of I-to to positive potential, therefore a higher membrane potential was required to activate I-to. CONCLUSION: I-to, a major K+ channel current in human atrial cells, is blocked by 4-AP.