title: Species-dependent hemodynamic effects of adenosine A3-receptor agonists IB-MECA and Cl-IB-MECA.
abstract: The purpose of this study was to compare the hemodynamic effects of the adenosine A3-receptor agonists N6-(3-iodobenzyl)-9-[5-(methylcarbamoyl)-beta-D-ribofuranosyl]aden ine (IB-MECA) and 2-chloro-N6-(3-iodobenzyl)-9-[5-(methylcarbamoyl)-beta-D-ribofu ranosy l]adenine (Cl-IB-MECA) in isolated rat and rabbit hearts and in the intact, open-chest pig. Isolated hearts perfused with Krebs-Henseleit buffer at a constant pressure (70 mmHg) were treated with 50 nM of either IB-MECA or Cl-IB-MECA. Neither IB-MECA nor Cl-IB-MECA altered ventricular function or heart rate in the isolated rat and rabbit hearts, and neither agent altered coronary flow in the rabbit. However, 2 min of IB-MECA treatment in the isolated rat heart increased coronary flow by 25%, an effect that did not exhibit tachyphylaxis. The IB-MECA-induced coronary dilation was only partially attenuated by the adenosine A3-receptor antagonist MRS-1191 (50 nM). IB-MECA-induced coronary dilation was completely blocked by the adenosine A2a-receptor antagonist 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2, 4-triazolo[1,5-c]pyrimidine (Sch-58261, 50 nM). Cl-IB-MECA (50 nM) did not increase coronary flow in the rat, but 100 nM did increase flow by 18%. In pentobarbital sodium-anesthetized pigs IB-MECA (5 micrograms/kg iv) decreased systemic blood pressure and increased pulmonary artery pressure, effects that did exhibit tachyphylaxis. These results illustrate that adenosine A3-receptor agonists produce species-dependent effects, which in the rat heart appear to be caused by adenosine A2a-receptor activation.
authors.affiliation: Department of Surgery and Vascular Biology Research Group, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA. rlasley@pop.uky.edu
authors.forename: R D
authors.initials: RD
authors.lastname: Lasley
authors.forename: P
authors.initials: P
authors.lastname: Narayan
authors.forename: M S
authors.initials: MS
authors.lastname: Jahania
authors.forename: E L
authors.initials: EL
authors.lastname: Partin
authors.forename: K R
authors.initials: KR
authors.lastname: Kraft
authors.forename: R M
authors.initials: RM
authors.lastname: Mentzer
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects; D004095:Dihydropyridines / Q000494:pharmacology; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011743:Pyrimidines / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D013552:Swine; D014230:Triazoles / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: C098657:5-amino-7-(2-phenylethyl)-2-(2-furyl)pyrazolo(4,3-e)-1,2,4-triazolo(1,5-c)pyrimidine; D004095:Dihydropyridines; C107728:MRS 1191; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011743:Pyrimidines; D014230:Triazoles; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; D000241:Adenosine; C090034:2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide