Related Experiment Videos
Potassium does not mimic EDHF in rat mesenteric arteries
J M Doughty1, J P Boyle, P D Langton
1Department of Physiology, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
British Journal of Pharmacology
|July 6, 2000
Summary
Potassium ions (K(+)) and endothelium-derived hyperpolarizing factors (EDHF) both relax rat mesenteric arteries. However, their distinct sensitivities to barium and ouabain suggest K(+) acts differently from EDHF.
Area of Science:
- Vascular Physiology
- Endothelium-Dependent Vasodilation
- Ion Channel Function
Background:
- Endothelium-derived hyperpolarizing factor (EDHF) is a key mediator of vasodilation in small arteries.
- The role of extracellular potassium ions ([K+](o)) as a potential EDHF has been investigated, but its precise contribution remains unclear.
- Understanding the mechanisms of vasodilation is crucial for managing cardiovascular diseases.
Purpose of the Study:
- To compare the vasodilatory effects of acetylcholine (ACh)-stimulated EDHF with those of elevated extracellular potassium ([K+](o)) in rat mesenteric arteries.
- To elucidate the distinct pharmacological profiles of EDHF and [K+](o)-mediated relaxation.
- To investigate the involvement of myo-endothelial gap junctions in ACh-induced vasodilation.
Main Methods:
- Experiments were conducted on pressurized and isometrically mounted rat mesenteric arteries.
- Vasodilatation/relaxation was assessed in response to acetylcholine (ACh) and elevated extracellular potassium ([K+](o)).
- Pharmacological agents including barium (Ba(2+)), ouabain, and gap junction inhibitors (Gap-27, 18-alpha-glycyrrhetinic acid) were used to probe the underlying mechanisms.
Main Results:
- ACh induced vasodilation in all arteries, while elevated [K+](o) only dilated a subset.
- Barium ions (Ba(2+)) differentially affected ACh- and [K+](o)-mediated responses, inhibiting the latter more significantly.
- Ouabain and gap junction inhibitors impaired ACh-induced vasodilation, suggesting a role for myo-endothelial gap junctions in EDHF-mediated responses.
Conclusions:
- Both EDHF and elevated [K+](o) contribute to vasodilation in rat mesenteric arteries, but exhibit different sensitivities to Ba(2+) and ouabain.
- Extracellular potassium ions may act as a relaxing factor, but its mechanism appears distinct from EDHF.
- Myo-endothelial gap junctions play a significant role in EDHF-mediated vasodilation.