Effect of aminophylline on coronary reactive and functional hyperaemic response in conscious dogs.

This study was undertaken to determine whether adenosine release from myocardial cells plays a role in coronary reactive and functional vasomotion. Reactive hyperaemic blood flow responses to 10 s complete occlusions and 400 ms diastolic occlusions of the left circumflex coronary artery and to the vasomotor responses to the increased cardiac demand following ventricular extra-activation were examined in a chronic, heart-blocked dog preparation during a control period and following intravenous bolus administration of aminophylline (5 mg X kg-1). Aminophylline administration resulted in a 19% decrease in the blood flow debt repayment ratio of 10 s reactive hyperaemic responses compared with the control period. However, administration of aminophylline had no effect on the coronary vascular response to 400 ms diastolic occlusions or to ventricular extra-activations. These observations indicate that adenosine may play a role in the coronary vascular response to prolonged interventions but that other factors, as yet unidentified, may be implicated in the beat-to-beat regulation of coronary vascular resistance.