Characteristics of transient outward K+ current in human atrial cardiomyocytes.
OBJECTIVE
To study the properties of transient outward potassium current (Ito) in human atrial myocytes.


METHODS
The patch-clamp whole-cell recording techniques were used. When the calcium inward current was blocked by CdCl2 (0.1 mmol.L-1), the transient outward potassium current (Ito) was recorded by depolarizing cells.


RESULTS
The current was voltage dependent, it was activated quickly and inactivated rapidly too. 4-Aminopyridine (4-AP) 10 mmol.L-1 (a selective blocker of Ito) blocked the current completely. The IC50 (95% confidence limits) of 4-AP on Ito were 0.67 (0.58-0.80) mmol.L-1, 4-AP 1 mmol.L-1 shifted the activation curve of Ito to positive potential, therefore a higher membrane potential was required to activate Ito.


CONCLUSIONS
Ito, a major K+ channel current in human atrial cells, is blocked by 4-AP.
Xu
W H
WH
Department of Pharmacology, Peking Union Medical College, Beijing, China.
Li
W
W
Yue
H W
HW
Wang
X L
XL
D015761:4-Aminopyridine / Q000494:pharmacology*; D006325:Heart Atria / Q000166:cytology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*
D015221:Potassium Channels; D015761:4-Aminopyridine