title: Analysis of the influence of nucleotidases on the apparent activity of exogenous ATP and ADP at P2Y1 receptors.
abstract: 1. ADP is a potent agonist of rat and human P2Y1 purinoceptors. ATP is a weak competitive antagonist. This study analyses the situation in which P2Y1 receptors are exposed to ATP in the presence of exogenous ecto-nucleotidases (apyrases) that have high or low ATPase/ADPase activity ratio. 2. Rat brain capillary endothelial cells of the B10 clone express P2Y1 receptors that couple to intracellular Ca2+ mobilization. They have low endogenous ecto-ATPase and ecto-ADPase activities. 3. ATP did not raise intracellular Ca2+ in B10 cells. Addition of apyrases III or VII (1 u ml(-1)) to ATP treated cells induced large intracellular Ca2+ transients. Apyrases had no action in the absence of ATP. 4. A 1 u ml(-1) apyrase III solution generated 20 microM ADP from 0.1 mM ATP within 15 s. This concentration of ADP was sufficient to produce maximal activation of P2Y1 receptors. 5. ATP was a full agonist of P2Y1 receptors in the presence of 1 u ml(-1) apyrase III. Dose response curves for the apparent actions of ATP were bell shaped in the presence of 0.1 u ml(-1) apyrase III. Apyrase III did not alter ADP dose response curves when coincubated with ADP for 15 s. 6. Apyrase VII (1 u ml(-1)) shifted dose response curves for the actions of ADP to larger concentrations. It induced a bell shaped ATP dose response curve. 7. Results suggest that ATPDases prevent P2Y1 receptor activation by degrading ADP but may contribute to P2Y1 receptor activation by generating ADP from ATP.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Université de Nice-Sophia Antipolis, Valbonne, France.
authors.forename: P
authors.initials: P
authors.lastname: Vigne
authors.forename: J P
authors.initials: JP
authors.lastname: Breittmayer
authors.forename: C
authors.initials: C
authors.lastname: Frelin
mesh_terms: D000244:Adenosine Diphosphate / Q000096:biosynthesis* / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000502:physiology; D002196:Capillaries / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology; D009708:Nucleotidases / Q000494:pharmacology*; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000187:drug effects*; D058472:Receptors, Purinergic P2Y1
chemical_list: C546382:P2RY1 protein, human; C546384:P2ry1 protein, rat; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D009708:Nucleotidases; D000251:Adenosine Triphosphatases