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Consistent parallel relationships among myocardial oxygen consumption, coronary blood flow, and pericardial infusate
Insights
Adenosine levels in the heart adjust with oxygen demand, influencing coronary blood flow. This study shows adenosine concentration parallels myocardial oxygen consumption and blood flow changes, regardless of the stimulus.
Area of Science:
- Cardiovascular Physiology
- Biochemistry
Background:
- Coronary blood flow regulation is crucial for matching oxygen supply to myocardial demand.
- Adenosine is a potential mediator of this autoregulation, but its role requires further investigation.
Purpose of the Study:
- To determine if interstitial fluid adenosine concentration changes in parallel with myocardial oxygen consumption and coronary blood flow.
- To investigate if adenosine mediates the unique response of coronary blood flow to altered cardiac work, irrespective of the stimulus.
Main Methods:
- Measurements of coronary blood flow, myocardial oxygen consumption, and pericardial infusate adenosine concentration in anesthetized dogs.
- Experimental conditions included aortic constriction, vagal stimulation, atrial pacing, and infusions of calcium chloride, norepinephrine, and isoproterenol.
- Analysis of linear relationships between these parameters under various stimuli and after beta-blockade.
Main Results:
- Significant alterations in myocardial oxygen consumption and coronary blood flow were consistently accompanied by changes in pericardial infusate adenosine concentration.
- Strong linear relationships were observed among myocardial oxygen consumption, coronary blood flow, and adenosine concentration across all experimental conditions.
- These relationships remained consistent and were unaffected by beta-blockade.
Conclusions:
- Adenosine production appears to respond to changes in myocardial oxygen consumption independently of the specific stimulus.
- The resulting changes in interstitial fluid adenosine concentration likely play a key role in regulating coronary blood flow to maintain oxygen supply-demand balance.
- Adenosine is a critical factor in the heart's ability to autoregulate its own blood supply.
Abstract:
Coronary blood flow responds uniquely to changes in myocardial demand, regardless of the stimulus. If adenosine mediates this response, interstitial fluid adenosine concentration should also change in parallel with myocardial oxygen consumption and coronary blood flow during alterations of cardiac work. We tested this hypothesis by measuring coronary blood flow, myocardial oxygen consumption, and the concentration of adenosine in pericardial infusates, an index of interstitial fluid adenosine concentration, during six experimental conditions and control states in anesthetized, open-chest dogs. Significant alterations of myocardial oxygen consumption and coronary blood flow during aortic constriction, vagal stimulation, atrial pacing, or intravenous infusion of calcium chloride, norepinephrine, or isoproterenol were accompanied by significant alterations in pericardial infusate adenosine concentration. Significant linear relationships were determined among myocardial oxygen consumption, coronary blood flow, and pericardial infusate adenosine concentration for each of the experimental stimuli and their paired control values. There were no significant differences among the six different conditions for any of these relationships. In addition, these relationships were not altered by beta-blockade in five dogs subjected to aortic constriction and calcium infusion. Although beta-blockade may alter the effects of a stimulus, myocardial oxygen consumption, coronary blood flow, and adenosine all are affected proportionately. The results suggest that adenosine production responds to alterations of myocardial oxygen consumption independently of the stimulus which produces the change in oxygen demand, and the resultant change in interstitial fluid adenosine concentration may initiate the change in coronary blood flow to maintain the balance between oxygen supply and demand.