title: Differential activation of protein kinase C between ischemic and pharmacological preconditioning in the rabbit heart.
abstract: The objective of the present study was to investigate the differential activation of protein kinase C between ischemic (IPC) and pharmacological preconditioning (PPC) in the rabbit heart. Control, IPC, diazoxide (Diaz), and chelerythrine (Chel)+IPC groups underwent prolonged coronary artery occlusion (CAO) for 30 minutes followed by 180 minutes' reperfusion (protocol I). In protocol II, sham, IPC-only, Diaz-only, and Chel+IPC-only groups did not undergo prolonged CAO. IPC was induced with 4 cycles of 5-min regional ischemia and 10-min reperfusion before prolonged CAO. Diaz (5 mg/kg) was administered 30 min before prolonged CAO. Chel (5 mg/kg) was administered 5 min before the IPC procedure. Infarct size was determined by tetrazolium staining. Assessment of protein kinase C (PKC) isoforms from a left ventricular (LV) sample was conducted by western blotting. Apoptosis in situ was determined by TUNEL assay. The infarction area in the IPC (11.6 +/- 1.0%) and Diaz (19.5 +/- 3.8%) groups was reduced significantly (p< 0.01, p< 0.05) relative to the control group (40.0 +/- 3.8%). The reduction by IPC was abolished by pretreatment with Chel. Apoptosis was significantly decreased (p< 0.01) in the IPC and diazoxide groups compared with the control and Chel+IPC groups (control: 4.78 +/- 0.56% vs. IPC: 2.00 +/- 0.38% vs. Diaz: 2.20 +/- 0.32% vs. Chel+IPC: 4.32 +/- 0.41%) and DNA laddering was attenuated in the IPC and Diaz groups. Membrane PKC-epsilon levels in the IPC and Diaz groups increased significantly relative to the control and Chel+IPC groups. Membrane PKC-epsilon levels in the IPC-only group showed greater increases than the Diaz-only and Chel+IPC-only groups. These findings suggest that whereas PPC suppresses apoptosis when diazoxide opens mitochondrial K(ATP) channels and then activates PKC-epsilon through ischemia-reperfusion, IPC activates PKC-epsilon in the particulate fraction prior to continuous ischemia-reperfusion. We concluded that the difference between IPC and PPC appears to consist in the difference in the timing of PKC-epsilon activation, though both IPC and PPC provide the cardioprotection in ischemia-reperfusion injury.
authors.affiliation: Department of Cardiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Kahoku, Ishikawa 920-0293, Japan. shinkubo@kanazawa-med.ac.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Okubo
authors.forename: Yujirou
authors.initials: Y
authors.lastname: Tanabe
authors.forename: Nakaba
authors.initials: N
authors.lastname: Fujioka
authors.forename: Kenji
authors.initials: K
authors.lastname: Takeda
authors.forename: Noboru
authors.initials: N
authors.lastname: Takekoshi
mesh_terms: D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002316:Cardiotonic Agents / Q000494:pharmacology; D003213:Conditioning, Psychological; D053938:DNA Fragmentation; D003981:Diazoxide / Q000494:pharmacology*; D004357:Drug Synergism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016678:Genome; D006321:Heart / Q000187:drug effects*; D006439:Hemodynamics; D019157:Ischemic Preconditioning, Myocardial; D007527:Isoenzymes / Q000378:metabolism; D009203:Myocardial Infarction / Q000473:pathology; D009206:Myocardium / Q000201:enzymology; D032383:Myocytes, Cardiac; D010617:Phenanthridines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D016277:Ventricular Function, Left
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010617:Phenanthridines; C016299:chelerythrine; D011493:Protein Kinase C; D003981:Diazoxide