Adenosine 5'-(2-fluorodiphosphate) is not a selective P2Y purinoceptor agonist in the rabbit jugular vein.
The relaxant properties of the putative selective P2Y agonist adenosine 5'-(2-fluorodiphosphate) (ADP-beta-F) and its structural analog adenosine 5'-(2-thiodiphosphate) have been investigated in the rabbit precontracted jugular vein preparation. In tissues with intact endothelium, ADP-beta-F produced a multiphasic agonist concentration/effect curve made up of two vasorelaxant components which were kinetically and pharmacologically distinct. The higher potency phase (p[A50] 5.58 +/- 0.13), characterized by slow, tonic responses, was retained after endothelial denudation and blocked by the selective P1 purinoceptor antagonist 8-sulphophenyltheophylline. The lower potency phase (p[A50] 3.98 +/- 0.07), characterized by fast, phasic responses, was abolished by endothelial denudation and is presumed to be mediated at P2Y purinoceptors. By contrast, the agonist concentration/effect curve to adenosine 5'-(2-dithiophosphate) in endothelium-intact tissues appear monophasic and was unaffected by 8-sulphophenyltheophylline (p[A50] 6.86 +/- 0.12), although endothelial denudation revealed a secondary P1-induced relaxant component (p[A50] 5.73 +/- 0.20). This study demonstrates that in the rabbit jugular vein, relaxant responses to ADP-beta-F are mediated primarily by activation of P1 purinoceptors, and it is, therefore, invalid to regard ADP-beta-F as a selective probe for P2Y purinoceptors, whereas adenosine 5'-(2-thiodiphosphate) does show some selectivity for this receptor.
Wood
B E
BE
Department of Pharmacology, Fisons Research and Development Laboratories, Loughborough, Leicestershire, England.
O'Connor
S E
SE
Leff
P
P
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D007601:Jugular Veins / Q000187:drug effects; D008297:Male; D011817:Rabbits; D011983:Receptors, Purinergic / Q000187:drug effects*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
D011983:Receptors, Purinergic; C087189:2-fluoro-ADP; D000244:Adenosine Diphosphate; C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline