Adenosine metabolism in canine myocardial reactive hyperemia.

In pentobrabital-anesthetized open chest dogs, myocardial adenosine content is elevated by 5 or 15 seconds of left coronary artery occlusion and falls exponentially to control levels during reactive hyperemia. The rate constants for adenosine dissipation are (mean +/- SEM): -0.08 +/- 0.01 and -0.034 +/- 0.007 sec-1 after 5- and 15-second occlusion, respectively. Kinetic analysis of the reactive hyperemia flow curves (Circ Res 14/15 (suppl I): 81-85, 1963) predicts rates of -0.069 +/- 0.009 sec-1 and -0.04 +/- 0.009 sec-1, indicating that changes in adenosine levels can account for the way coronary flow changes during this response. The log (dose-) response curve relating reactive hyperemia flow to tissue adenosine concentration has a steeper slope and is half-maximal at a lower adenosine concentration than the dose-response curve obtained by intracoronary infusions of adenosine in oxygenated hearts, indicating that the coronary vasoactivity of adenosine is enhanced during reactive hyperemia. This could ex...