EFFECTS OF SURAMIN ON THE CONCENTRATION-RESPONSE RELATIONSHIP OF ALPHA,BETA-METHYLENE ATP ON THE MOUSE VAS-DEFERENS

1 The effect of suramin on the concentration-effect curve for the contractile response of the isolated mouse vas deferens to alpha,beta-methylene ATP (alpha,beta-meATP) was investigated. 2 The concentration-response curve to alpha,beta-meATP had a consistent discontinuity at about 3 x 10(-6) M, giving it a biphasic appearance. 3 Suramin in a dose-dependent, reversible manner both shifted the curve to the right and at the same time elevated the maximum response. 4 The P2y inhibitor Reactive Blue 2, on the other hand, both shifted the curve to the left and elevated the maximum response. 5 These results show that alpha,beta-meATP in this preparation is an agonist both at excitatory, presumably P2x receptors and inhibitory P2y receptors, and that suramin antagonizes both effects.