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1. The effect of pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on the relaxant response to adenine nucleotides was examined in the carbachol-contracted guinea-pig taenia coli and rat duodenum, two tissues possessing P2y-purinoceptors. In addition, in the taenia coli PPADS was investigated for its effect on relaxations evoked by adenosine,(More)
1. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), an inhibitor of P2X-purinoceptor-mediated responses in rabbit vas deferens, was investigated for its ability to antagonize contractions evoked by alpha,beta-methylene ATP (alpha,beta-MeATP), carbachol and electrical field stimulation in the rabbit urinary bladder detrusor muscle. 2. PPADS.(More)
Ecto-ATPase activity of Xenopus oocytes was studied by measuring the production of inorganic phosphate (Pi) from the breakdown of extracellular ATP. Enzyme activity involved Ca2+/Mg2+-dependent and Ca2+/Mg2+-independent dephosphorylation of ATP. Ca2+/Mg2+-dependent ecto-ATPase was active over a limited range of 0.01–1.0 mM ATP, while Ca2+/Mg2+-independent(More)
1. The effects of NF023, the symmetrical 3'-urea of 8-(benzamido)naphthalene-1,3,5-trisulphonic acid), and its parent compound suramin were investigated on vasoconstrictor responses to alpha, beta-methylene ATP in rabbit isolated saphenous artery and vasodilator responses to ATP in noradrenaline-precontracted rabbit isolated thoracic aorta. 2. In rabbit(More)
1. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), a P2-purinoceptor antagonist, was investigated for its ability to antagonize: (1) P2X-purinoceptor-mediated contractions of the rabbit central ear artery and saphenous artery evoked by either alpha,beta-methylene ATP (alpha,beta-MeATP) or electrical field stimulation (EFS); (2)(More)
Ecto-nucleotidase activity was studied on primary cultures of guinea-pig vas deferens smooth muscle cells by measuring the inorganic phosphate (Pi) production using ATP as a substrate. The ecto-nucleotidase was insensitive to ouabain, oligomycin, sodium azide, p-nitrophenyl phosphate and B-glycerophosphate. Enzyme activity was highly dependent on either(More)
1. In the guinea-pig urinary bladder and vas deferens, several alpha,beta-unsaturated sulphones and phosphonium salts that were tested inhibited ecto-ATPase activity. The sulphones were more active in the bladder but the phosphonium salts were more effective in the vas deferens. 2. These compounds either potentiated or inhibited purinergic contractile(More)
The aim of the present study was to examine the effects of a number of P2-purinoceptor antagonists on degradation of adenine nucleotides by Xenopus laevis oocyte ecto-nucleotidase. Folliculated oocytes readily metabolize all three naturally-occurring nucleotides, the order of preferential substrates being ATP >ADP > AMP. The degradation of ATP and ADP was(More)
Study of P2-purinoceptor subtypes has been difficult due to the lack of potent and selective ligands. With the goal of developing high affinity P2-purinoceptor-selective agonist, we have synthesized a series of analogues of adenine nucleotides modified on the purine ring as chain-extended 2-thioethers or as N6-methyl-substituted compounds. Chemical(More)