What question did this study set out to answer?

To quantitatively evaluate whether adenosine mediates the local metabolic regulation of coronary blood flow during exercise hyperemia.

Adenosine is not responsible for local metabolic control of coronary blood flow in dogs during exercise

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Why the study?

Does adenosine receptor blockade alter coronary blood flow and myocardial oxygen consumption during exercise in dogs?

Population

Dogs chronically instrumented with catheters in the aorta and coronary sinus, and a flow probe on the…

Comparison

Adenosine receptor blockade with either… vs Control vehicle without adenosine receptor…

Design

Preclinical

Authors

No immediate clinical implications from canine data; challenges adenosine mediation of exercise coronary flow and leaves its role open in humans.

To quantitatively evaluate whether adenosine mediates the local metabolic regulation of coronary blood flow during exercise hyperemia.
Chronically instrumented dogs (N=10) with aortic and coronary sinus catheters and circumflex coronary artery flow probes were assessed at rest and during graded treadmill exercise.
Hemodynamics, myocardial oxygen consumption, and interstitial adenosine concentrations were measured before and after adenosine receptor blockade using 8-PT or 8-PST.
Treadmill exercise increased myocardial oxygen consumption 4.2-fold, coronary blood flow 3.8-fold, and heart rate 2.5-fold, while estimated interstitial adenosine concentrations remained below the vasodilation threshold.
Adenosine receptor blockade with 8-PT or 8-PST did not significantly alter myocardial oxygen consumption or coronary blood flow at rest or during exercise, and adenosine levels failed to rise to overcome receptor blockade.

Does adenosine receptor blockade alter coronary blood flow and myocardial oxygen consumption during exercise in dogs?

Population

Dogs (n = 10) chronically instrumented with catheters in the aorta and coronary sinus, and a flow probe on the circumflex coronary artery.

Intervention

Adenosine receptor blockade with either 8-phenyltheophylline (8-PT) or 8-p-sulfophenyltheophylline (8-PST) during graded treadmill exercise.

Comparator

Control vehicle without adenosine receptor blockade during graded treadmill exercise.

Outcome

Coronary blood flow, myocardial oxygen consumption, heart rate, aortic pressure, and cardiac interstitial adenosine concentration.surrogate

This study demonstrates that adenosine is not responsible for local metabolic control of coronary blood flow during exercise in dogs.

Tune et al. (2000) studied this question.

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No immediate clinical implications from canine data; challenges adenosine mediation of exercise coronary flow and leaves its role open in humans.