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 P-2 purinoceptor antagonist, on the vasodilat or response to adenosine 5'-triphosphate (ATP), 2-methylthio-ATP (2-me SATP) and adenosine were examined in the Sprague-Dawley rat coronary v asculature 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 by suramin. 8-(p-Sulpho phenyl)theophylline (8-PSPT) did not affect the relaxant response to A TP and 2-meSATP at a concentration that significantly inhibited the re sponse to adenosine. It is concluded that 2-meSATP acts via P-2Y purin oceptors while ATP appears to be acting largely through a different me chanism. It is not acting via a P-1 purinoceptor because ATP was not i nhibited by the P-1 purinoceptor antagonist 8-PSPT.