On the possible role of adenosine in the hypoxia-induced alterations of the electrical and mechanical activity of the atrial myocardium.

The effects of adenosine on transmembrane potential and myocardial contractility were compared with those of hypoxia in electrically driven left atrial preparations of guinea-pigs. The amplitude and duration of action potential, contractile force and maximum rate of rise of tension development were decreased by both adenosine and hypoxia. Both the adenosine- and hypoxia-induced changes could readily be prevented by aminophylline, a competitive antagonist of adenosine. Serious changes of transmembrane atrial potential due to long-lasting hypoxia could also be reversed by aminophylline. On the basis of the present results it is assumed that in acute myocardial hypoxia the increased tissue level of adenosine might contribute to the functional impairment of the atrial myocardium.