Effect of adenosine deaminase inhibitors on myocardial reactive hyperaemia following brief coronary occlusions

Effect of two agents of adenosine deaminase inhibitor, 8-azaguanine and adenine, on myocardial reactive hyperaemia was tested in the anaesthetised open-chest dog. Reactive hyperaemic flow response of the circumflex coronary artery was observed following 5, 10, 15, 20 and 30 s coronary occlusions before, during and after infusion of 8-azaguanine and adenine, which are known as adenosine deaminase inhibitors. Intracoronary infusion of 8-azaguanine and adenine caused the minimum increase in the baseline coronary flow. Both the nucleic acids shifted the dose response curve of adenosine to the left. 8-azaguanine enhanced volume response of flow at all occlusion intervals tested. The infused dose of adenine also intensified volume response of flow after 5, 15, 20 and 30 s occlusions. Fifteen minutes after termination of the nucleic acid infusions, the reactive hyperaemia returned towards control levels. The results suggest that 8-azaguanine and adenine enhance myocardial reactive hyperaemia possibly by inhibiting adenosine deaminase to degradate myocardial interstitial adenosine to inosine.