title: Adenosine A(2a)-receptor activation increases contractility in isolated perfused hearts.
abstract: Adenosine A(2a)-receptor activation enhances shortening of isolated cardiomyocytes. In the present study the effect of A(2a)-receptor activation on the contractile performance of isolated rat hearts was investigated by recording left ventricular pressure (LVP) and the maximal rate of LVP development (+dP/dt(max)). With constant-pressure perfusion, adenosine caused concentration-dependent increases in LVP and +dP/dt(max), with detectable increases of 4.1 and 4.8% at 10(-6) M and maximal increases of 12.0 and 11.1% at 10(-4) M, respectively. The contractile responses were prevented by the A(2a)-receptor antagonists chlorostyryl-caffeine and aminofuryltriazolotriazinyl-aminoethylphenol (ZM-241385) but were not affected by the beta(1)-adrenergic antagonist atenolol. The adenosine A(1)-receptor antagonist dipropylcyclopentylxanthine and pertussis toxin potentiated the positive inotropic effects of adenosine. The A(2a)-receptor agonists ethylcarboxamidoadenosine and dimethoxyphenyl-methylphenylethyl-adenosine also enhanced contractility. With constant-flow perfusion, 10(-5) M adenosine increased LVP and +dP/dt(max) by 5.5 and 6.0%, respectively. In the presence of the coronary vasodilator hydralazine, adenosine increased LVP and +dP/dt(max) by 7.5 and 7.4%, respectively. Dipropylcyclopentylxanthine potentiated the adenosine contractile responses with constant-flow perfusion in the absence and presence of hydralazine. These increases in contractile performance were also antagonized by chlorostyryl-caffeine and ZM-241385. The results indicate that adenosine increases contractile performance via activation of A(2a) receptors in the intact heart independent of beta(1)-adrenergic receptor activation or changes in coronary flow.
authors.affiliation: Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Monahan
authors.forename: D R
authors.initials: DR
authors.lastname: Sawmiller
authors.forename: R A
authors.initials: RA
authors.lastname: Fenton
authors.forename: J G
authors.initials: JG
authors.lastname: Dobson
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D004357:Drug Synergism; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D010477:Perfusion; D037342:Pertussis Toxin; D011312:Pressure; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1 / Q000502:physiology*; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D000319:Adrenergic beta-Antagonists; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; D014665:Vasodilator Agents; D010566:Virulence Factors, Bordetella; D014970:Xanthines; C056426:CGS 24012; D019830:Adenosine-5'-(N-ethylcarboxamide); D001262:Atenolol; C051360:1,3-dipropyl-8-cyclopentylxanthine; D037342:Pertussis Toxin; D000241:Adenosine