The novel heteromeric bivalent ligand SB9 potently antagonizes P2Y(1) receptor-mediated responses.
Effects of 6-[(4,6,8-trisulfo-1-naphthyl)iminocarbonyl-1, 3-(4-methylphenylene)iminocarbonyl-1, 3-phenylene-azo]-pyridoxal-5'-phosphate (SB9), a heterodimeric bivalent ligand consisting of pyridoxal-5'-phosphate and the suramin monomer, were studied on contractions of the rat vas deferens elicited by alpha beta-methylene ATP (alpha beta meATP; mediated by P2X(1)-like receptors), contractions of the guinea-pig ileal longitudinal smooth muscle elicited by adenosine 5'-O-(2-thiodiphosphate) (ADP beta S mediated by P2Y(1)-like receptors), and the degradation of ATP by ecto-nucleotidases in folliculated Xenopus laevis oocytes. SB9 (0.1-10 microM) antagonized contractile responses produced by alpha beta meATP or ADP beta S in a concentration-dependent manner. Schild analysis yielded linear regression lines of unit slope, indicating competitive antagonism. From the rightward shifts of the agonist concentration-response curves pA(2) values of 6.05+/-0.13 (vas deferens) and 6.98+/-0.07 (ileum) were derived. In both preparations, SB9 behaved as a slow onset, slow offset antagonist. Incubation of three oocytes in the presence of ATP produced an increase in inorganic phosphate (P(i)) over a 30-min period, which amounted to 35.1+/-1.9 microM P(i) from 100 microM ATP. SB9 (10-1000 microM) reduced this degradation (pIC(50)=4.33+/-0.10). The results illustrate that SB9 is a high-affinity P2Y(1) receptor antagonist with a remarkable selectivity for P2Y(1) vs. P2X(1) receptors (about 10-fold) and ecto-nucleotidases (447-fold). These properties make it unique among the pyridoxal-5'-phosphate and suramin derivatives reported to date.
Lambrecht
G
G
Department of Pharmacology, Biocentre Niederursel, University of Frankfurt, Marie-Curie-Str. 9, D-60439, Frankfurt/M., Germany. lambrecht@em.uni-frankfurt.de
Ganso
M
M
Bäumert
H G
HG
Spatz-Kümbel
G
G
Hildebrandt
C
C
Braun
K
K
Mutschler
E
E
D015720:5'-Nucleotidase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D058472:Receptors, Purinergic P2Y1; D013498:Suramin / Q000031:analogs & derivatives* / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects; D014982:Xenopus laevis
C413694:6-((4,6,8-trisulfo-1-naphthyl)iminocarbonyl-1,3-(4-methylphenylene)iminocarbonyl-1,3-phenyleneazo)pyridoxal-5'-phosphate; D008024:Ligands; C546384:P2ry1 protein, rat; D010975:Platelet Aggregation Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D058472:Receptors, Purinergic P2Y1; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase