Key Points
- Determine whether myocardial adenosine content and coronary sinus plasma adenosine concentration correlate with coronary vascular resistance during treadmill exercise.
- Monitored conscious dogs during rest and 7 minutes of treadmill exercise at 5 mi/h on a 20% slope, producing a threefold increase in cardiac work.
- Measured myocardial adenosine content, coronary sinus plasma adenosine concentration, coronary vascular resistance, and myocardial hypoxia markers including lactate metabolism and coronary sinus oxygen tension.
- Exercise elevated myocardial adenosine from 1.35 ± 0.54 to 8.18 ± 0.60 nmol/g and coronary sinus plasma adenosine from 108 ± 16 to 184 ± 18 nmol/l, while coronary vascular resistance dropped from 1.07 ± 0.13 to 0.69 ± 0.08 mmHg·ml⁻¹·min·100 g.
- Coronary vascular resistance correlated negatively with both myocardial adenosine (r = -0.74, P < 0.01) and coronary sinus adenosine (r = -0.83, P < 0.01), with tissue and sinus adenosine correlating positively (r = 0.77, P < 0.05).
- Sustained lactate uptake, low tissue lactate, an unchanged lactate-pyruvate ratio, and stable coronary sinus oxygen tension confirmed the absence of myocardial hypoxia during exercise.
Structured PICO
IInterventionTreadmill exercise (5 mi/h for 7 min on a 20% slope)
OOutcomeRelation between myocardial adenosine content, coronary sinus plasma concentration, and coronary vascular resistancesurrogate
In conscious dogs, exercise-induced increases in myocardial and coronary sinus adenosine correlate with decreased coronary vascular resistance, supporting adenosine's role in regulating coronary blood flow during metabolic activity.