The effect of suramin on vasodilator responses to ATP and 2-methylthio-ATP in the Sprague-Dawley rat coronary vasculature

The effect of suramin, a P₂ purinoceptor antagonist, on the vasodilator response to adenosine 5′-triphosphate (ATP), 2-methylthio-ATP (2-meSATP) and adenosine were examined in the Sprague-Dawley rat coronary vasculature using the Langendorff heart preparation. Relaxation induced by 2-meSATP was significantly inhibited by suramin. Only responses to low doses of adenosine and ATP were inhibited bu suramin. 8-(p-Sulphophenyl)theophylline (8-PSPT) did not affect the relaxant response to ATP and 2-meSATP at a concentration that significantly inhibited the response to adenosine. It is concluded that 2-meSATP acts via P_2Y purinoceptors while ATP appears to be acting largely through a different mechanism. It is not acting via a P₁ purinoceptor because ATP was not inhibited by the P₁ purinoceptor antagonist 8-PSPT.