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Endothelial cell signaling during conducted vasomotor responses
Kim A Dora1, Jun Xia, Brian R Duling
1Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, VA 22906-0011, USA.
Summary
Electrical signals, not just calcium, rapidly spread along arteriole walls, controlling blood vessel responses. This electrical coupling in endothelial cells explains how blood flow is quickly regulated throughout the vessel.
Area of Science:
- Vascular biology
- Physiology
- Cell signaling
Background:
- Vasomotor responses in arterioles are rapid and spread along vessel walls.
- The mechanisms of signal transmission, such as electrical currents or calcium (Ca2+) spread via gap junctions, are not fully understood.
Purpose of the Study:
- To investigate the roles of electrical signaling and Ca2+ in mediating rapid vasomotor responses along arterioles.
- To differentiate between electrical coupling and Ca2+ signaling as the primary mode of signal transmission.
Main Methods:
- Isolated, cannulated, and perfused hamster cheek pouch arterioles were used.
- Fluo 3 and di-8-ANEPPS were employed for real-time measurement of intracellular Ca2+ concentration ([Ca2+]i) and membrane potential in endothelial cells, respectively.
- Photometric techniques measured changes in [Ca2+]i and membrane potential following localized stimulation with acetylcholine (ACh) or potassium chloride (KCl).
Main Results:
- Acetylcholine (ACh) stimulation caused localized increases in endothelial cell [Ca2+]i and hyperpolarization, preceding rapid, widespread vasodilation.
- Membrane potential changes spread longitudinally along the arteriole, preceding vasodilation at both stimulated and distant sites.
- Potassium chloride (KCl) stimulation induced widespread depolarization followed by vasoconstriction, with observed [Ca2+]i increases at distant sites.
- Electrical coupling was supported as the primary mechanism for rapid signal transmission along the arteriole.
Conclusions:
- Rapid vasomotor responses in arterioles are primarily mediated by the spread of electrical signals (changes in membrane potential) along the vessel wall.
- While Ca2+ signaling plays a role, particularly in modulating responses, electrical coupling appears to be the dominant mechanism for rapid, long-distance signal propagation.
- The close proximity of endothelial and smooth muscle cells allows for superimposed Ca2+ signaling, which fine-tunes the overall vasomotor response.