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Endothelium-derived relaxing factor participates in the transmural distribution of coronary bloodflow
1Department of Pathophysiology, Faculty of Medicine, University of Chile, Santiago.
Insights
Endothelium-derived relaxing factor (EDRF) influences coronary blood flow distribution. Inhibiting EDRF synthesis altered flow, particularly enhancing subendocardial flow during reactive hyperemia.
Area of Science:
- Cardiovascular Physiology
- Coronary Circulation
- Endothelial Function
Background:
- Endothelium-derived relaxing factor (EDRF) is crucial for regulating coronary vascular tone.
- The specific role of EDRF in the transmural distribution of coronary blood flow remains unclear.
- Understanding EDRF's role is vital for comprehending coronary hemodynamics.
Purpose of the Study:
- To investigate the role of EDRF in the transmural distribution of coronary blood flow.
- To examine EDRF's influence during both steady basal flow and reactive hyperemia in the canine left ventricular wall.
Main Methods:
- Mongrel dogs were utilized, with circumflex coronary flow measured by electromagnetic flowmetry.
- Transmural flow distribution was assessed using radioactive microspheres across four left ventricular wall layers.
- EDRF synthesis was inhibited using N-omega-nitro-L-arginine (NNLA) to observe effects on basal and hyperemic flow.
Main Results:
- Inhibition of EDRF synthesis significantly decreased steady basal coronary flow (22.3%).
- While flow decreased in all layers, the reduction was proportionally less in the subendocardium.
- During reactive hyperemia, NNLA administration reduced peak flow magnitude but relatively enhanced subendocardial flow.
Conclusions:
- EDRF plays a significant role in regulating coronary blood flow.
- EDRF is involved in the differential distribution of coronary blood flow across the left ventricular wall.
- Findings suggest EDRF contributes to maintaining subendocardial perfusion, especially during hyperemia.
Objective:
To study the role of endothelium-derived relaxing factor (EDRF)--which participates in the regulation of coronary vascular tone, but has an unknown role in the transmural distribution of coronary flow--in transmural coronary flow distribution during steady basal flow and during reactive hyperemia in the left ventricular wall of the dog.
Design:
Sixteen mongrel dogs of either sex weighing between 14 and 24 kg were anesthetized with sodium pentobarbital. The lungs were mechanically ventilated and the thoraces were opened. Circumflex coronary flow was measured with an electromagnetic flowmeter, and its transmural distribution across four layers of the left ventricular wall was measured with radioactive microspheres. Measurements were done during steady basal flow and during peak reactive hyperemia before and after the inhibition of the EDRF synthesis with N-omega-nitro-L-arginine (NNLA). Mean aortic and systolic left ventricular pressures and heart rate were kept constant, and left ventricular end-diastolic pressure increased by only 3.3 mmHg during reactive hyperemia.
Main Results:
NNLA produced a mean decrease of steady basal flow of 22.3 +/- 0.9% (P < 0.01). Flow decreased in all layers of the wall; the decrease, however, was proportionally less in the subendocardium (P < 0.05). During reactive hyperemia (before NNLA), flow was redistributed to the subendocardium (compared with steady basal flow). Administration of NNLA reduced the magnitude of peak reactive flow to all layers in the wall, showing a relative enhancement of flow in the subendocardium.
Conclusions:
These results suggest that the EDRF participates in the regulation of coronary bloodflow and its distribution across the left ventricular wall.