adp-beta-s and 8-(4-sulfophenyl)theophylline

The possibility was tested that endogenous ATP released upon alpha(1)-adrenoceptor activation causes relaxation of the rat vas deferens smooth muscle. ATP, 2-methylthio ATP and adenosine relaxed the vas deferens precontracted with 80 mM K(+). The metabolically stable P2 receptor agonists alpha,beta-methylene ATP (alpha,beta-MeATP) and adenosine 5'-O-(2-thiodiphosphate) (ADPbetaS) had little or no effect. The adenosine P1 receptor antagonist 8-(para-sulfophenyl)theophylline did not significantly affect the response to ATP. The P2 receptor antagonist reactive blue 2 markedly reduced the relaxation (by up to 73%); suramin, pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and acid blue 129 caused no change. ATP, but not alpha,beta-MeATP, also attenuated contractions elicited by noradrenaline at resting tension; reactive blue 2 blocked the inhibitory effect of ATP. Reactive blue 2, by itself, enhanced the response to noradrenaline (by up to 36%); suramin, PPADS and acid blue 129 caused no change. In the presence of the ATP-degrading enzymes apyrase and nucleotide pyrophosphatase, the facilitatory effect of reactive blue 2 was lost. Apyrase, by itself, enhanced the response to noradrenaline (by 13%). The results indicate that endogenous ATP, released from rat vas deferens smooth muscle upon alpha(1)-adrenoceptor stimulation, causes relaxation. The site of action of ATP is not a typical smooth muscle P2Y receptor.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Apyrase; Dose-Response Relationship, Drug; In Vitro Techniques; Male; Muscle Relaxation; Norepinephrine; Nucleotides; Potassium; Purinergic P1 Receptor Antagonists; Pyridoxal Phosphate; Pyrophosphatases; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-1; Suramin; Theophylline; Thionucleotides; Triazines; Vas Deferens; Vasoconstrictor Agents

We studied the role of adenosine and P2 receptors in the pelvic nerve stimulation-induced penile tumescence in anesthetized dogs. A local intracavernous injection of adenosine induced the tumescence, which was abolished by intracavernous 8-(p-sulfophenyl)theophylline (8-SPT), an unspecific adenosine receptor antagonist, and by 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-yl amino]ethyl)phenol (ZM241385), an adenosine A(2A) receptor antagonist. ATP also induced the tumescence, which was diminished by 8-SPT, but not by reactive blue-2, a P2 receptor antagonist. Neither intracavernous beta, gamma-meATP nor ADP(beta)S, P2X and P2Y receptor agonists, induced tumescence. N(G)-nitro-L-arginine (L-NAME), a nitric oxide synthase inhibitor, and T-1032, a phosphodiesterase type V inhibitor, had no effects on the tumescence induced by adenosine. 8-SPT and reactive blue-2 had no effects on the tumescence induced by pelvic nerve stimulation. These results show that although exogenous adenosine and ATP induce tumescence, neither the adenosine nor the P2 receptor is involved in the tumescence induced by pelvic nerve stimulation in anesthetized dogs.

Topics: Adenosine; Adenosine Diphosphate; Adenosine Triphosphate; Anesthesia; Animals; Dogs; Dose-Response Relationship, Drug; Enzyme Inhibitors; Injections, Intravenous; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Penile Erection; Penis; Purinergic P2 Receptor Agonists; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2; Theophylline; Thionucleotides; Triazines; Triazoles

1 The human P2Y11 receptor is coupled to both the phosphoinositide and the cyclic AMP pathways. A pharmacological characterization of the recombinant human P2Y11 receptor has been conducted following stable expression in two different cell lines: the 1321N1 astrocytoma cells for inositol trisphosphate measurements and the CHO-K1 cells for cyclic AMP assays. The rank order of potency of a series of nucleotides was almost identical for the two pathways: ATPgammaS approximately BzATP > dATP > ATP > ADPbetaS > 2MeSATP. 2 ADPbetaS, AMPalphaS and A3P5PS behaved as partial agonists of the human P2Y11 receptor. At high concentrations, these three nucleotides were able to partially inhibit the ATP response. 3 Suramin was a more potent antagonist than reactive blue 2, whereas pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid was completely inactive. The P2Y11 receptor proved to be sensitive to suramin in a competitive way with an apparent Ki value of 0.82+/-0. 07 microM. 4 The ATP derivative AR-C67085 (2-propylthio-beta, gamma-dichloromethylene-D-ATP), a potent inhibitor of ADP-induced platelet aggregation, was the most potent agonist of the P2Y11 receptor, among the various nucleotides tested. 5 The pharmacological profile of the recombinant human P2Y11 receptor is closely similar to that of the cyclic AMP-coupled P2 receptor recently described in HL-60 cells, suggesting that it is the same receptor.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; CHO Cells; Cricetinae; Cyclic AMP; Dose-Response Relationship, Drug; Humans; Inositol 1,4,5-Trisphosphate; Phosphoadenosine Phosphosulfate; Purinergic P2 Receptor Agonists; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2; Recombinant Fusion Proteins; Suramin; Theophylline; Thionucleotides; Time Factors; Triazines; Tumor Cells, Cultured

1. Both adenosine and adenosine 5'-triphosphate (ATP) (10 microM and 100 microM) relaxed 10 microM acetylcholine (ACh)-induced contraction of rat bladder strips, which was completely antagonized by 100 microM 8-(p-sulphophenyl) theophylline. In dog bladder neither adenosine nor ATP inhibited ACh-induced contraction. 2. P2x-purinoceptor agonists contracted both rat and dog bladder strips with the potency order of alpha,beta-MeATP > ATP > ADP. 3. Alpha,beta-MeADP (100 microM) induced a contraction of the rat bladder strip even after desensitization of P2x-purinoceptors but failed to contract the dog bladder strip. 4. 2-MeSATP (1 microM to 300 microM) concentration-dependently induced contraction of rat bladder strips; this contraction was significantly inhibited after desensitization of P2x-purinoceptors. Cibacron blue 3GA (100 microM) antagonized the drug at concentrations lower than 30 microM, whereas it augmented the response to the drug at concentrations above 30 microM. 5. ADP beta S (1 microM to 1 mM) concentration-dependently induced contraction of rat bladder strips after desensitization of P2x-purinoceptors; a contraction which was significantly antagonized by cibacron blue 3GA (100 microM). 6. It is concluded that three subtypes of purinoceptors, P1 (mediating relaxation), and P2x and another type of P2 (mediating contraction), exist in rat urinary bladder smooth muscle, whereas a single subtype of the receptor, P2x-purinoceptor (mediating contraction) occurs in dog urinary bladder smooth muscle.

Topics: Acetylcholine; Adenosine; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Dogs; Female; In Vitro Techniques; Male; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Protein Synthesis Inhibitors; Rats; Rats, Wistar; Receptors, Purinergic P1; Receptors, Purinergic P2; Theophylline; Thionucleotides; Triazines; Urinary Bladder