State-dependent blockade of human ether-a-go-go-related gene (hERG) K(+) channels by changrolin in stably transfected HEK293 cells.
OBJECTIVE
To study the effect of changrolin on the K(+) channels encoded by the human ether-a-go-go-related gene (hERG).


METHODS
hERG channels were heterologously stably expressed in human embryonic kidney 293 cells, and the hERG K(+) currents were recorded using a standard whole-cell patch-clamp technique.


RESULTS
Changrolin inhibited hERG channels in a concentration-dependent and reversible manner (IC(50)=18.23 mumol/L, 95% CI: 9.27-35.9 mumol/L; Hill coefficient=-0.9446). In addition, changrolin shifted the activation curve of hERG channels by 14.3+/-1.5 mV to more negative potentials (P<0.01, n=9) but did not significantly affect the steady-state inactivation of hERG (n=5, P>0.05). The relative block of hERG channels by changrolin was close to zero at the time point of channel opening by the depolarizing voltage step and quickly increased afterwards. The maximal block was achieved in the inactivated state, with no further development of the open channel block. In the "envelope of tails" experiments, the time constants of activation were found to be 287.8+/-46.2 ms and 174.2+/-18.4 ms, respectively, for the absence and presence of 30 mumol/L changrolin (P<0.05, n=7). The onset of inactivation was accelerated significantly by changrolin between -40 mV and +60 mV (P<0.05, n=7).


CONCLUSIONS
The results demonstrate that changrolin is a potent hERG blocker that preferentially binds to hERG channels in the open and inactivated states.
Chen
Wei-hai
WH
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
Wang
Wen-yi
WY
Zhang
Jie
J
Yang
Ding
D
Wang
Yi-ping
YP
D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002460:Cell Line; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors*; D006801:Humans; D020128:Inhibitory Concentration 50; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011799:Quinazolines / Q000008:administration & dosage / Q000494:pharmacology*; D014162:Transfection
D000889:Anti-Arrhythmia Agents; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D011799:Quinazolines; C022128:changrolin