title: Endogenous adenosine attenuates myocardial stunning by antiadrenergic effects exerted during ischemia and not during reperfusion.
abstract: The effect of adenosine receptor blockade and adrenergic blockade on myocardial stunning [left anterior descending coronary artery (LAD) occluded for 10 min and reperfused for 180 min] was studied in 38 open-chest cats. A control group (Control) was compared with two other groups in which adenosine receptors were blocked by 8-phenyltheophylline (7.5 mg/kg) before reperfusion (8-PT-R) or before ischemia (8-PT-I). Group A, in which adrenergic receptors were blocked (doxazosin 200 micrograms/kg + propranolol 1 mg/kg), was compared with group A + 8-PT-I, in which both adenosine and adrenergic receptors were blocked before coronary artery occlusion. Regional systolic function assessed by sonomicrometry in the LAD perfused area recovered less in 8-PT-I (55 +/- 5% recovery) as compared with Control (87 +/- 9%) and 8-PT-R (89 +/- 8%), which indicates that adenosine receptor blockade during ischemia increases stunning. Functional recovery was similar in Control, group A (96 +/- 5%), and group A + 8-PT-I (87 +/- 5%), which demonstrates that if adrenergic receptors are blocked, adenosine receptor blockade during ischemia does not increase stunning. These results may indicate that the cardioprotective effects of endogenous adenosine are mediated through antiadrenergic effects exerted during coronary artery occlusion.
authors.affiliation: Department of Surgery, University of Bergen, Norway.
authors.forename: S E
authors.initials: SE
authors.lastname: Rynning
authors.forename: H
authors.initials: H
authors.lastname: Brunvand
authors.forename: S
authors.initials: S
authors.lastname: Birkeland
authors.forename: E
authors.initials: E
authors.lastname: Hexeberg
authors.forename: K
authors.initials: K
authors.lastname: Grong
mesh_terms: D000241:Adenosine / Q000502:physiology*; D000818:Animals; D002415:Cats; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology; D017292:Doxazosin / Q000494:pharmacology; D006321:Heart / Q000503:physiopathology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology*; D011433:Propranolol / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D058915:Purinergic P1 Receptor Antagonists; D011433:Propranolol; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine; D017292:Doxazosin