Short-time adenosine deaminase interventions upon underperfused rat hearts in vitro--a test for the role of adenosine in the coronary flow control.

Spontaneously beating rat heart Langendorff preparations, perfused with Tyrode solution under low flow conditions (1.62 +/- 0.47 ml/min at 55 mmHg), were used to investigate the role of adenosine in the coronary flow control, by means of adenosine-deaminase injections into the perfusion system. Adenosine deaminase did not influence the control coronary flow, but significantly reduced autoregulation, hypoxic vasodilation, reactive hyperemia and functional adrenaline-induced hyperemia. All these effects, excepting the hypoxic vasodilation reduction, dependent upon the moment of enzyme injection during the experiment. Under the mentioned conditions adenosine seems to be responsible for more than half of the autoregulation of the coronary flow. Adenosine deaminase completely abolished reactive hyperemia during control perfusion but only delayed it under adrenaline perfusion.