On the suitability of adenosine 3'-phosphate 5'-phosphosulphate as a selective P2Y receptor antagonist in intact tissues.
Agonist and antagonist effects of the putative P2Y1 receptor antagonist adenosine 3'-phosphate 5'-phosphosulphate (PAPS) were studied in intact tissues. In the carbachol-precontracted guinea-pig taenia coli, PAPS caused prominent relaxation (EC50 3.3 microM). The response was attenuated by the P2 receptor antagonists 4,4'-diisothiocyanatostilbene-2,2'-disulphonate (DIDS) and reactive red 2 with apparent Kd values (0.27 and 0.29 microM) indicating that PAPS acts through the non-P2Y receptor, which is the site of action of alpha,beta-methylene ATP (alpha,beta-MeATP) in the taenia coli. Incubation with PAPS (10-100 microM) attenuated the P2Y receptor-mediated relaxation caused by 5'-O-(2-thiodiphosphate) (ADPbetaS); PAPS (100 microM) also attenuated the relaxation caused by alpha,beta-MeATP, as well as the alpha1-adrenoceptor-mediated response to noradrenaline. In the noradrenaline-precontracted rat aorta, PAPS caused minor relaxation (EC50 24.7 microM), which was reduced by the P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2',5'-disulphonate (iso-PPADS; 1 microM), indicating that PAPS activates endothelial P2Y receptors. Incubation with PAPS (10 and 100 microM) attenuated the P2Y receptor-mediated relaxation caused by ADPbetaS; PAPS (100 microM) also attenuated the P2U receptor-mediated relaxation caused by UTP and the muscarine receptor-mediated response to acetylcholine. In rat vas deferens, PAPS (100 microM) attenuated the P2X receptor-mediated contraction elicited by alpha,beta-MeATP but did not alter the alpha1-adrenoceptor-mediated response to noradrenaline. The results indicate that PAPS attenuates P2Y receptor-mediated relaxation in intact tissues. However, due to its limited subtype selectivity and non-P2 receptor effects, the nucleotide is not a suitable antagonist for this subtype.
Bültmann
R
R
Pharmakologisches Institut, Freiburg i. Br., Germany.
Tuluc
F
F
Starke
K
K
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D003106:Colon / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D010724:Phosphoadenosine Phosphosulfate / Q000494:pharmacology*; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000502:physiology; D058472:Receptors, Purinergic P2Y1; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology
C546384:P2ry1 protein, rat; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D010724:Phosphoadenosine Phosphosulfate