Abstract
The multifunctional Ca++/calmodulin-dependent protein kinase II (CaM kinase) mediates Ca++-induced augmentation of L-type Ca++ current (ICa); therefore it may act as a proarrhythmic signaling molecule during early afterdepolarizations (EADs) due to ICa. To investigate the hypothesis that ICa-dependent EADs are favored by CaM kinase activation EADs were induced with clofilium in isolated rabbit hearts. All EADs were rapidly terminated with ICaantagonists. Hearts were pretreated with the CaM kinase inhibitor KN-93 or the inactive analog KN-92 (0.5 μM) for 10 min before clofilium exposure. EADs were significantly suppressed by KN-93 (EADs present in 4/10 hearts) compared to KN-92 (EADs present in 10/11 hearts) (P = .024). There were no significant differences in parameters favoring EADs such as monophasic action potential duration or heart rate in KN-93- or KN-92-treated hearts. CaM kinase activity in situincreased 37% in hearts with EADs compared to hearts without EADs (P = .015). This increase in CaM kinase activity was prevented by pretreatment with KN-93. In vitro, KN-93 potently inhibited rabbit myocardial CaM kinase activity (calculatedKi ≤ 2.58 μM), but the inactive analog KN-92 did not (Ki > 100 μM). The actions of KN-93 and KN-92 on ICa and other repolarizing K+currents did not explain preferential EAD suppression by KN-93. These data show a novel association between CaM kinase activation and EADs and are consistent with the hypothesis that the ICa and CaM kinase activation both contribute to EADs in this model.
Footnotes
-
Send reprint requests to: Dr. Mark E. Anderson, Division of Cardiology, Vanderbilt University School of Medicine, 315 Medical Research Building II, Nashville, TN 37232-6300.
-
This work was supported by National Institutes of Health Grant HL03727 (M.E.A.), a Cardiac Arrhythmia Research and Education Foundation, Inc. (Irvine, CA) grant (M.E.A.) the Stanford Cardiac and Cellular Electrophysiology Program Grant HL07740 from the National Institutes of Health (M.E.A.), a grant from the S.K.B. Foundation (Sunnyvale, CA) (R.J.S.) and National Institutes of Health Grant GM30179 (H.S.).
- Abbreviations:
- CaM
- calmodulin
- CaM kinase
- multifunctional Ca2+/calmodulin dependent protein kinase II
- DAD
- delayed afterdepolarization
- EAD
- early afterdepolarization
- LV
- left ventricle
- LVDP
- left ventricular developed pressure
- MAP
- monophasic action potential
- [Ca++]i
- intracellular Ca++
- ICa
- L-type Ca++ current
- Vm
- cell membrane potential KN-93, 2-[N-(2-hidroxyethyl)-N-(4-methoxy-benzenesulfonyl)]-amino-N-(4-chlorocinnamyl)-N-methylbenzylamine
- KN-9Z
- (Z-N-(4-methoxybenzenesulfonyl)-amino-N-(4-chlorocinnamyl)-N-methylbenzylamine
- AP
- action potential
- DMSO
- dimethyl sulfoxide
- DTT
- dithiothreitol
- EGTA
- ethylene glycol-bis(β-aminoethyl ether)N,N,N′,N′-tetraacetic acid
- EDTA
- ethylenediaminetetraacetic acid
- PIPES
- piperazine-N,N′-bis[z-ethanesulfonic acid]
- 1
- 4-piperazinediethanesulfonic acid
- RV
- right ventricle
- ECG
- electrocardiogram
- LVDP
- LV developed pressure
- BSA
- bovine serum albumin
- 4-AP
- 4-aminopyridine
- Received January 21, 1998.
- Accepted June 25, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|
Log in using your username and password
Pay Per Article - You may access this article (from the computer you are currently using) for 1 day for US$35.00
Regain Access - You can regain access to a recent Pay per Article purchase if your access period has not yet expired.
In this issue
KN-93, an Inhibitor of Multifunctional Ca++/Calmodulin-Dependent Protein Kinase, Decreases Early Afterdepolarizations in Rabbit Heart
