title: A biphasic response to adenosine in the coronary vasculature of the K(+)-arrested perfused rat heart.
abstract: Biphasic vasodilatory responses to adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) were observed in the coronary vasculature of K(+)-arrested perfused rat hearts. Dose-response data for both agonists were best represented by two-site models. For adenosine, two sites with negative log ED50 (pED50) values of 8.1 +/- 0.1 (mean +/- S.E.M) and 5.2 +/- 0.1 were obtained, mediating 31 +/- 2% and 69 +/- 2% of the total response. In the presence of 8-phenyltheophylline, the vasodilatory response to adenosine remained best fitted to a two-site model with pED50 values of 7.0 +/- 0.2 and 5.4 +/- 0.2. The relative contribution of each site to the total response remained unchanged. For NECA, pED50 values of 9.6 +/- 0.1 and 6.8 +/- 0.2 were obtained, representing 48 +/- 3% and 52 +/- 3% of the sites, respectively. In contrast, ATP produced a monophasic response with a pED50 value of 8.8 +/- 0.1. These results provide evidence of adenosine receptor and response heterogeneity in the in situ coronary vasculature.
authors.affiliation: Rotary Centre for Cardiovascular Research, School of Science, Griffith University, Nathan, Queensland, Australia.
authors.forename: F A
authors.initials: FA
authors.lastname: Harden
authors.forename: G J
authors.initials: GJ
authors.lastname: Harrison
authors.forename: J
authors.initials: J
authors.lastname: Headrick
authors.forename: L R
authors.initials: LR
authors.lastname: Jordan
authors.forename: R J
authors.initials: RJ
authors.lastname: Willis
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006324:Heart Arrest, Induced; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D010477:Perfusion; D011188:Potassium; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D017208:Rats, Wistar; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D058906:Purinergic P1 Receptor Agonists; D014665:Vasodilator Agents; D019830:Adenosine-5'-(N-ethylcarboxamide); D000255:Adenosine Triphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine; D011188:Potassium