Evidence for an adenosine receptor on the surface of dog coronary myocytes

Adenosine and theophylline were linked covalently to oxidized stachyose to produce compounds too large to penetrate cell membranes. These compounds were used in two conscious and six open-chest anesthetized dogs to test the hypothesis that there is an adenosine receptor on the surface of the coronary myocyte. Intracoronary infusions of the adenosine derivative produced dose-dependent coronary vasodilation which was antagonized by theophylline; two types of theophylline derivative antagonized the coronary vasodilatory action of adenosine. Although these results show that both adenosine and theophylline exert their coronary effects at the surface of the smooth muscle cells, this evidence does not establish that they are competing for a common receptor.