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Myocardial adenosine and coronary resistance during increased cardiac performance
Insights
This study reveals that higher myocardial adenosine levels correlate with lower coronary vascular resistance in dogs, suggesting adenosine
Area of Science:
- Cardiovascular Physiology
- Biochemistry
Background:
- Adenosine plays a crucial role in regulating myocardial blood flow.
- Understanding the relationship between adenosine and coronary vascular resistance is key to comprehending cardiac function.
Purpose of the Study:
- To investigate the correlation between myocardial adenosine content and coronary vascular resistance.
- To explore the role of adenosine in the local control of coronary circulation during increased cardiac performance.
Main Methods:
- Open-chest dog model.
- Cardiac performance augmentation via aortic constriction or isoproterenol infusion.
- Microsphere tracer technique for coronary blood flow measurement.
- Measurement of myocardial adenosine content and coronary vascular resistance.
Main Results:
- A significant negative correlation (r = 0.77) was observed between coronary vascular resistance and the logarithm of myocardial adenosine content.
- No transmural gradient in adenosine content was found in control and aortic-constricted groups.
- A significant adenosine gradient was noted in the isoproterenol-infused group, associated with decreased coronary input pressure.
- Absence of myocardial ischemia was confirmed by low lactate content and stable coronary sinus blood pH.
Conclusions:
- Adenosine is implicated in the local regulation of coronary circulation.
- Increased cardiac performance is associated with changes in myocardial adenosine levels and coronary vascular resistance.
- Findings support adenosine's role in modulating coronary blood flow under physiological stress.
Abstract:
The relation between myocardial adenosine content and coronary vascular resistance was studied in the open-chest dog. Cardiac performance was increased by aortic constriction or by intravenous infusion of isoproterenol. Coronary blood flow was measured by the microsphere tracer technique. In control animals, adenosine content and coronary vascular resistance were 0.22 +/- 0.03 nmol/g and 1.9 +/- 0.11 mmHg . ml-1 . min . 100 g, respectively. A range of myocardial oxygen consumptions of 5.3-24 ml O2 . min-1 . 100 g-1 was elicited. This was associated with a range of coronary blood flows of 33-166 ml . min-1 . 100 g-1. There was a significant negative correlation between coronary vascular resistance and the log of the myocardial adenosine content (r = 0.77). There was no transmural gradient in adenosine content in the control and aortic-constricted groups, but there was a significant adenosine gradient in the isoproterenol-infused group in which coronary input pressure was decreased. The hearts were not ischemic, as indicated by low myocardial lactate contents and a stable coronary sinus blood pH. These results provide support for a role of adenosine in the local control of the coronary circulation during increased cardiac performance.