Inhibition of Coronary Vasodilating Action of Dipyridamole and Adenosine by Aminophylline in the Dog

Experiments were performed to determine (1) whether intravenously administered aminophylline inhibits the coronary vasodilating effects of intravenous or intracoronary administration of dipyridamole or adenosine and (2) whether aminophylline locally administered in the coronary artery inhibits the vasodilating action of adenosine given intravenously or injected into the coronary artery. Coronary vasodilator responses to dipyridamole or adenosine were determined before and after administration of aminophylline. Intravenous aminophylline was found to inhibit coronary vasodilatation induced by intravenous or intracoronary dipyridamole or adenosine. After intravenous aminophylline, adenosine administered intravenously or into the coronary artery was 2.5 to 4 times less effective in inducing coronary vasodilatation. Aminophylline injected locally into the coronary artery was also effective in inhibiting coronary vasodilatation induced by intravenous and intracoronary adenosine. The mechanism of this inhibitory phenomenon has not been elucidated.