Interaction of ropivacaine with cloned cardiac Kv4.3/KChIP2.2 complexes.
BACKGROUND
Inhibition of cardiac K channels by local anesthetic may contribute to QTc interval prolongation of the electrocardiogram and induction of ventricular arrhythmia. The transient outward current Ito has been identified as a toxicologically relevant target of bupivacaine. S(-)-ropivacaine has been developed as a safer alternative to bupivacaine. The effects of S(-)-ropivacaine on Ito have not been investigated. In human ventricular myocardium, Ito is formed by Kv4.3 and KChIP2.2 subunits. Therefore, the aim of this study was to establish the effects of S(-)-ropivacaine on human Kv4.3/KChIP2.2 channels.


METHODS
Kv4.3/KChIP2.2 complementary DNA cloned from human heart was transiently transfected in Chinese hamster ovary cells. The pharmacologic effects of S(-)-ropivacaine were investigated with the patch clamp method.


RESULTS
Ropivacaine inhibited Kv4.3/KChIP2.2 channels in a concentration-dependent, stereospecific, and reversible manner. The IC50 value of S(-)-ropivacaine for inhibition of the charge conducted by Kv4.3/KChIP2.2 channel was 117 +/- 21 microm (n = 30). The local anesthetic accelerated macroscopic current decline with an IC50 value of 77 +/- 11 microm (n = 30). It shifted the midpoint of channel activation into the depolarizing direction, and it slowed recovery from inactivation without altering steady state inactivation. Kv4.3 channels are more sensitive to the inhibitory effect than Kv4.3/KChIP2.2 channels.


CONCLUSIONS
: The results are consistent with the idea that ropivacaine, by blocking Kv4.3/KChIP2.2 from the open state, interferes with the gating modifying effects of KChIP2.2 on Kv4.3 channels. Inhibition of Kv4.3/KChIP2.2 channels by the local anesthetic may contribute to the deterioration of cardiac function during events of intoxication.
Friederich
Patrick
P
Department of Anesthesiology, University Hospital Hamburg Eppendorf, Germany. patrick.friederich@zmnh.uni-hamburg.de
Solth
Anna
A
D000577:Amides / Q000737:chemistry / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007536:Isomerism; D007700:Kinetics; D051605:Kv Channel-Interacting Proteins; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D000077212:Ropivacaine; D051672:Shal Potassium Channels; D013237:Stereoisomerism; D014162:Transfection
D000577:Amides; D000779:Anesthetics, Local; C497021:KCND3 protein, human; C496752:KCNIP2 protein, human; D051605:Kv Channel-Interacting Proteins; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D051672:Shal Potassium Channels; D000077212:Ropivacaine