title: A3 adenosine receptor agonist IB-MECA reduces myocardial ischemia-reperfusion injury in dogs.
abstract: We examined the effect of the A3 adenosine receptor (AR) agonist IB-MECA on infarct size in an open-chest anesthetized dog model of myocardial ischemia-reperfusion injury. Dogs were subjected to 60 min of left anterior descending (LAD) coronary artery occlusion and 3 h of reperfusion. Infarct size and regional myocardial blood flow were assessed by macrohistochemical staining with triphenyltetrazolium chloride and radioactive microspheres, respectively. Four experimental groups were studied: vehicle control (50% DMSO in normal saline), IB-MECA (100 microg/kg iv bolus) given 10 min before the coronary occlusion, IB-MECA (100 microg/kg iv bolus) given 5 min before initiation of reperfusion, and IB-MECA (100 microg/kg iv bolus) given 10 min before coronary occlusion in dogs pretreated 15 min earlier with the ATP-dependent potassium channel antagonist glibenclamide (0.3 mg/kg iv bolus). Administration of IB-MECA had no effect on any hemodynamic parameter measured including heart rate, first derivative of left ventricular pressure, aortic pressure, LAD coronary blood flow, or coronary collateral blood flow. Nevertheless, pretreatment with IB-MECA before coronary occlusion produced a marked reduction in infarct size ( approximately 40% reduction) compared with the control group (13.0 +/- 3.2% vs. 25.2 +/- 3.7% of the area at risk, respectively). This effect of IB-MECA was blocked completely in dogs pretreated with glibenclamide. An equivalent reduction in infarct size was observed when IB-MECA was administered immediately before reperfusion (13.1 +/- 3.9%). These results are the first to demonstrate efficacy of an A3AR agonist in a large animal model of myocardial infarction by mechanisms that are unrelated to changes in hemodynamic parameters and coronary blood flow. These data also demonstrate in an in vivo model that IB-MECA is effective as a cardioprotective agent when administered at the time of reperfusion.
authors.affiliation: Cardiovascular Research Center, Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA. jauchamp@mcw.edu
authors.forename: John A
authors.initials: JA
authors.lastname: Auchampach
authors.forename: Zhe-Dong
authors.initials: ZD
authors.lastname: Ge
authors.forename: Tina C
authors.initials: TC
authors.lastname: Wan
authors.forename: Jeannine
authors.initials: J
authors.lastname: Moore
authors.forename: Garrett J
authors.initials: GJ
authors.lastname: Gross
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D000758:Anesthesia; D000818:Animals; D002316:Cardiotonic Agents / Q000378:metabolism / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D004285:Dogs; D007457:Iodine Radioisotopes; D009203:Myocardial Infarction / Q000188:drug therapy; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy*; D058906:Purinergic P1 Receptor Agonists; D011869:Radioligand Assay; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000378:metabolism
chemical_list: D002316:Cardiotonic Agents; D007457:Iodine Radioisotopes; D058906:Purinergic P1 Receptor Agonists; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; C089722:N(6)-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide; D000241:Adenosine