Effect of aminophylline on coronary reactive hyperaemia following brief and long occlusion periods

The effects of an intracoronary aminophylline infusion, adjusted to give a constant concentration of 25 microgram.cm-3 coronary blood, on the reactive hyperaemic responses following coronary occlusion for 4, 10, and 25 heart beats were investigated in anaesthetised, open-chest dogs. The vasodilator effect of intracoronarily-administered adenosine and the hyperaemic response after coronary occlusion for 10 and 25 heart beats were both significantly diminished under the influence of aminophylline. However, the decrease in the coronary dilator effect of adenosine amounted to 80%, whereas the hyperaemic response was diminished by only 20%. The hyperaemic response following a coronary occlusion for only 4 heart beats remained unchanged. The present results obtained with aminophylline suggest at least a partial involvement of adenosine in mediating reactive hyperaemia after sufficiently long periods of coronary artery occlusion.