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Endothelium-medicated control of the coronary circulation. Exercise training-induced vascular adaptations
M H Laughlin1, R M McAllister, J L Jasperse
1Department of Veterinary Biomedical Sciences, University of Missouri, Columbia, USA.
Insights
The endothelium regulates coronary blood flow at rest and during exercise. Exercise training impacts endothelial function, but optimal training parameters for coronary adaptation remain unclear, especially in coronary heart disease (CHD).
Area of Science:
- Cardiovascular Physiology
- Endothelial Biology
- Exercise Physiology
Background:
- The endothelium plays a critical role in regulating coronary vascular function.
- Coronary blood flow is controlled by metabolic, myogenic, and endothelium-mediated mechanisms, with varying importance along the arterial tree.
Purpose of the Study:
- To review the endothelium's role in coronary vascular function at rest, during exercise, and in response to exercise training.
- To examine how coronary heart disease (CHD) affects endothelium-mediated control.
- To discuss the endothelium's role in regulating coronary vascular permeability.
Main Methods:
- Review of existing literature on endothelial function in the coronary circulation.
- Discussion of mechanisms controlling coronary blood flow, vascular resistance, and permeability.
- Analysis of the impact of exercise and exercise training on endothelial function.
Main Results:
- Endothelium-dependent vasodilation is key for resting coronary blood flow and conduit artery dilation during exercise.
- Atherosclerosis and CHD impair exercise-induced dilation, leading to vasoconstriction due to endothelial dysfunction.
- Exercise training alters endothelial control of coronary blood flow and microvessel permeability, though optimal training specifics are undefined.
Conclusions:
- The endothelium is crucial for normal coronary vascular function and is significantly impacted by CHD.
- Exercise training induces adaptive changes in endothelial function, but further research is needed to optimize training protocols.
- Endothelial control of vascular permeability is dynamic and influenced by exercise training, particularly relevant in the context of CHD.
Abstract:
This review discusses the role of the endothelium in the regulation of coronary vascular function. The role of endothelium-mediated mechanisms at rest, during exercise, in exercise training-induced adaptations of coronary function and in the presence of coronary heart disease (CHD) are examined. Mechanisms of control of coronary blood flow are briefly discussed with emphasis on endothelium-mediated control of vascular resistance. The concept that the relative importance of vascular control mechanisms differs as a function of position along the coronary arterial tree is developed and discussed. Metabolic, myogenic and endothelium-mediated control systems contribute in parallel to regulating coronary blood flow. The relative importance of these mechanisms varies throughout the coronary arterial tree. Endothelium-dependent vasodilation contributes to maintenance of resting coronary blood flow but the endothelium's role in dilation of small resistance arteries, thereby increasing coronary blood flow during exercise, remains in question. In contrast, the endothelium plays an essential role in dilation of the conduit coronary arteries during exercise. Atherosclerosis and CHD convert this exercise-induced dilation to a vasoconstriction, apparently due to endothelium dysfunction. Long term increases in physical activity and exercise training alter the control of coronary blood flow. Adaptations in endothelium-mediated control play a role in these changes. However, the effects of the mode, frequency, and intensity of exercise training bouts and duration of training on adaptive changes in endothelial function have not been established. The role of the endothelium in control of the permeability characteristics of the exchange vessels in the coronary circulation is discussed. Current evidence indicates that vascular permeability is a dynamic characteristic of the vessel wall that is controlled, at least in part, by endothelium-dependent phenomena. Also, preliminary results indicate that exercise training alters microvessel permeability and the control of permeability in the coronary circulation. Further research is needed to provide clarification of the effects of exercise training on coronary endothelial control of vascular resistance and vascular permeability in atherosclerosis and CHD.