Pharmacological characterization of a new purinergic receptor site in rabbit aorta.
1. The pharmacological properties of a vasodilating purine-activated receptor that is not a P1 or P2-purinoceptor were investigated. 2. In rabbit isolated thoracic aorta precontracted with noradrenaline, ATP induced a 50% relaxation at 0.25 mM (EC 50%); in the absence of endothelium, EC 50% was 2.5 mM. 3. Adenosine induced a relaxation that was not different in both the presence and absence of endothelium, being EC 50% 0.48 and 0.37 mM, respectively. 4. The potent and selective P2y-purinoceptor agonist 2-methylthio-ATP (0.03-10 microM) induced a relaxation only in the presence of endothelium. 5. In de-endothelialized aorta, 8-phenyltheophilline (8-PT: P1 antagonist) and 3,7-dimethyl-1-propargylxanthine (DMPX: A2 antagonist) did not antagonize ATP- and adenosine-induced relaxation. 6. The present data support the presence of a new site of action for purines in rabbit isolated thoracic aorta. 7. A P3 subtype of purinoceptor, that may be identified in the hypothesized "nucleotide" receptor, is proposed.
Chinellato
A
A
Department of Pharmacology, University of Padova, Italy.
Ragazzi
E
E
Pandolfo
L
L
Froldi
G
G
Caparrotta
L
L
Fassina
G
G
D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011817:Rabbits; D011983:Receptors, Purinergic / Q000187:drug effects*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
D011983:Receptors, Purinergic; D013873:Thionucleotides; D000255:Adenosine Triphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine; C008501:2-methylthio-ATP