title: Receptor and non-receptor-dependent mechanisms of cardioprotection with adenosine.
abstract: The relative roles of mitochondrial (mito) ATP-sensitive K(+) (mitoK(ATP)) channels, protein kinase C (PKC), and adenosine kinase (AK) in adenosine-mediated protection were assessed in Langendorff-perfused mouse hearts subjected to 20-min ischemia and 45-min reperfusion. Control hearts recovered 72 +/- 3 mmHg of ventricular pressure (50% preischemia) and released 23 +/- 2 IU/g lactate dehydrogenase (LDH). Adenosine (50 microM) during ischemia-reperfusion improved recovery (149 +/- 8 mmHg) and reduced LDH efflux (5 +/- 1 IU/g). Treatment during ischemia alone was less effective. Treatment with 50 microM diazoxide (mitoK(ATP) opener) during ischemia and reperfusion enhanced recovery and was equally effective during ischemia alone. A(3) agonism [100 nM 2-chloro-N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide], A(1) agonism (N(6)-cyclohexyladenosine), and AK inhibition (10 microM iodotubercidin) all reduced necrosis to the same extent as adenosine, but less effectively reduced contractile dysfunction. These responses were abolished by 100 microM 5-hydroxydecanoate (5-HD, mitoK(ATP) channel blocker) or 3 microM chelerythrine (PKC inhibitor). However, the protective effects of adenosine during ischemia-reperfusion were resistant to 5-HD and chelerythrine and only abolished when inhibitors were coinfused with iodotubercidin. Data indicate adenosine-mediated protection via A(1)/A(3) adenosine receptors is mitoK(ATP) channel and PKC dependent, with evidence for a downstream location of PKC. Adenosine provides additional and substantial protection via phosphorylation to 5'-AMP, primarily during reperfusion.
authors.affiliation: Heart Foundation Research Centre, School of Health Science, Griffith University Gold Coast Campus, Southport, Queensland 4217, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Peart
authors.forename: Laura
authors.initials: L
authors.lastname: Willems
authors.forename: John P
authors.initials: JP
authors.lastname: Headrick
mesh_terms: D000241:Adenosine / Q000008:administration & dosage* / Q000494:pharmacology; D000248:Adenosine Kinase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002316:Cardiotonic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004334:Drug Administration Schedule; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008929:Mitochondria, Heart / Q000378:metabolism; D017202:Myocardial Ischemia / Q000378:metabolism / Q000503:physiopathology*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology*; D015221:Potassium Channels / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D058906:Purinergic P1 Receptor Agonists; D020127:Recovery of Function
chemical_list: D002316:Cardiotonic Agents; D015221:Potassium Channels; D058906:Purinergic P1 Receptor Agonists; D000255:Adenosine Triphosphate; D000248:Adenosine Kinase; D011493:Protein Kinase C; D000241:Adenosine; D003981:Diazoxide