Suramin and reactive blue 2 are antagonists for a newly identified purinoceptor on rat megakaryocyte

The effects of purinoceptor antagonists on ATP‐induced oscillatory K⁺‐currents in rat isolated megakaryocytes were investigated. Both reactive blue‐2 (RB‐2), a selective antagonist of the P_2Y purinoceptor, at concentrations of 0.3–10 μm and suramin, a non‐selective P₂ purinoceptor antagonist, at 1–30 μm blocked the ATP‐induced oscillation in a concentration‐dependent manner. RB‐2 and suramin also blocked the ADP‐induced K⁺‐current oscillation at the same concentration range as in the case of ATP. However, both suramin and RB‐2 had no effect on thrombin‐ and inositol 1,4,5‐trisphosphate (IP₃)‐induced K⁺ current oscillation, indicating that they act as specific purinoceptor antagonists. Thus, the purinoceptors on megakaryocytes show the properties of the P₂ subtype according to their blockade by antagonists. 1994 British Pharmacological Society