title: Rapid component I(Kr) of cardiac delayed rectifier potassium currents in guinea-pig is inhibited by alpha(1)-adrenoreceptor activation via protein kinase A and protein kinase C-dependent pathways.
abstract: Ventricular tachyarrhythmias are often precipitated by physical or emotional stress, indicating a link between increased adrenergic stimulation and cardiac ion channel activity. Human ether-a-go-go related gene (hERG) potassium channels conduct the rapid component of delayed rectifier potassium current, I(kr), a crucial component for action potential repolarization. To evaluate the correlation between increased alpha(1)-adrenergic activity and the rapid component of cardiac I(kr), whole-cell patch-clamp recording was performed in isolated guinea-pig ventricular myocytes. Stimulation of alpha(1)-adrenoceptors using phenylephrine (0.1 nM-100 microM) reduced I(kr) current in a dose-dependent manner at 37 degrees C. Phenylephrine (0.1 microM) reduced I(kr) current to 66.83+/-3.16%. Chelerythrine (1 microM), a specific inhibitor of protein kinase C (PKC) completely inhibited the changes in I(kr) trigged by 0.1 microM phenylephrine. KT5720 (2.5 microM), a specific inhibitor of protein kinase A (PKA) partially inhibited the current decrease induced by 0.1 microM phenylephrine. Both chelerythrine and KT5720 drastically reduced the phenylephrine-induced effects, indicating possible involvement of PKC and PKA in the alpha(1)-adrenergic inhibition of I(kr). Our data suggest a link between I(kr) and the alpha(1)-adrenoceptor, involving activation of PKC and PKA in arrhythmogenesis.
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Wang
authors.forename: Dong-Jie
authors.initials: DJ
authors.lastname: Xu
authors.forename: Jing-Bo
authors.initials: JB
authors.lastname: Cai
authors.forename: Yuan-Zhu
authors.initials: YZ
authors.lastname: Huang
authors.forename: Jian-Gang
authors.initials: JG
authors.lastname: Zou
authors.forename: Ke-Jiang
authors.initials: KJ
authors.lastname: Cao
mesh_terms: D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D007700:Kinetics; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*
chemical_list: D053119:Benzophenanthridines; D002227:Carbazoles; D004791:Enzyme Inhibitors; D024661:Potassium Channels, Inwardly Rectifying; D011758:Pyrroles; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; C057416:KT 5720; C016299:chelerythrine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D011188:Potassium