title: Adenosine-mediated early preconditioning in mouse: protective signaling and concentration dependent effects.
abstract: OBJECTIVE
  Signaling in adenosine-mediated preconditioning is controversial. We examined roles of mitochondrial (mito) K(ATP) channels, protein kinase C (PKC) and nitric oxide (NO).
  
  
  METHODS
  Langendorff perfused C57/Bl6 mouse hearts were subjected to 20 min ischemia and 45 min reperfusion. Effects of adenosine-mediated preconditioning were assessed in the absence and presence of signaling inhibitors.
  
  
  RESULTS
  Control hearts recovered 70+/-2 mmHg ventricular pressure, and released 18.1+/-2.0 IU/g lactate dehydrogenase (LDH). Preconditioning with 10 microM adenosine limited necrosis (10.6+/-1.4 IU/g) without modifying contractility (72+/-2 mmHg) whereas 50 microM adenosine reduced necrosis (10.3+/-1.6 IU/g) and contractile dysfunction (91+/-2 mmHg). All protective effects of 10 and 50 microM adenosine were abrogated by mito K(ATP) channel blockade with 100 microM 5-hydroxydecanoate (5-HD) during the 'trigger' phase, but unaltered by PKC or NO synthase inhibition with 3 microM chelerythrine or 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME), respectively. Protection against necrosis was eliminated by 5-HD but unaltered by chelerythrine or L-NAME during the 'mediation' phase (ischemia-reperfusion). Reduced contractile dysfunction with 50 microM adenosine was partially sensitive to 5-HD and chelerythrine, and only eliminated by co-infusion of the inhibitors.
  
  
  CONCLUSIONS
  Adenosine-mediated preconditioning is dose-dependent with high level stimulation reducing contractile dysfunction in addition to necrosis. Preconditioning is triggered by a mito K(ATP) channel dependent process independently of PKC and NO. Subsequent protection against necrosis is also mediated by a mito K(ATP) channel dependent process independent of PKC and NO. In contrast, functional protection may be mediated by parallel mito K(ATP) and PKC dependent paths.
authors.affiliation: Heart Foundation Research Centre, School of Health Science, Griffith University Gold Coast Campus, Queensland 4217, Southport, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Peart
authors.forename: John P
authors.initials: JP
authors.lastname: Headrick
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D019271:Hypoxanthine / Q000494:pharmacology; D007288:Inosine / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008929:Mitochondria, Heart / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009336:Necrosis; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010477:Perfusion; D010617:Phenanthridines / Q000494:pharmacology; D010627:Phenethylamines / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019820:Xanthine / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D002121:Calcium Channel Blockers; D003652:Decanoic Acids; D004791:Enzyme Inhibitors; D006880:Hydroxy Acids; D010617:Phenanthridines; D010627:Phenethylamines; D015221:Potassium Channels; D018048:Receptors, Purinergic P2; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D019820:Xanthine; D019271:Hypoxanthine; D009569:Nitric Oxide; D007288:Inosine; D000244:Adenosine Diphosphate; C052853:5-hydroxydecanoic acid; C016299:chelerythrine; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D011493:Protein Kinase C; D000241:Adenosine; D003981:Diazoxide; D019331:NG-Nitroarginine Methyl Ester