These findings support the concept that hypoxia-induced coronary vasodilation is mediated by adenosine formed from the breakdown of myocardial adenine nucleotides.
In the presence of 8-azaguanine, an inhibitor of adenosine deaminase, adenosine appears in the perfusate of isolated cat and guinea pig hearts subjected to anoxia or severe hypoxia. With graded hypoxia the increase in coronary flow is roughly proportional to the sum of adenosine, inosine and hypoxanthine released from the hearts and inversely related to the oxygen tension of the perfusion fluid. Addition of epinephrine to oxygenated perfusion medium yields results similar to those obtained with hypoxia. These findings are compatible with the concept that vasodilation observed with hypoxia is due to adenosine formed from the breakdown of myocardial adenine nucleotides.
Katori et al. (1966) studied this question.