Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (KCa) and connexins: possible relationship to vasodilator function?
Article first published online: 24 OCT 2006
Journal of Anatomy
Volume 209, Issue 5, pages 689–698, November 2006
How to Cite
Sandow, S. L., Neylon, C. B., Chen, M. X. and Garland, C. J. (2006), Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (KCa) and connexins: possible relationship to vasodilator function?. Journal of Anatomy, 209: 689–698. doi: 10.1111/j.1469-7580.2006.00647.x
- Issue published online: 24 OCT 2006
- Article first published online: 24 OCT 2006
- Accepted for publication 30 August 2006
- cell coupling;
- gap junction;
- potassium channels;
- smooth muscle
Activation of endothelial cell small- (S) and intermediate- (I) conductance calcium-activated potassium channels (KCa) and current or molecular transfer via myoendothelial gap junctions underlies endothelium-derived hyperpolarization leading to vasodilation. The mechanism underlying the KCa component of vasodilator activity and the characteristics of gap junctions are targets for the selective control of vascular function. In the rat mesenteric artery, where myoendothelial gap junctions and connexin (Cx) 40 are critical for the transmission of the endothelial cell hyperpolarization to the smooth muscle, SKCa and IKCa provide different facets of the endothelium-derived hyperpolarization response, being critical for the hyperpolarization and repolarization phases, respectively. The present study addressed the question of whether this functional separation of responses may be related to the spatial localization of the associated channels? The distribution of endothelial SKCa and IKCa and Cx subtype(s) were examined in the rat mesenteric artery using conventional confocal and high-resolution ultrastructural immunohistochemistry. At the internal elastic lamina–smooth muscle cell interface at internal elastic lamina holes (as potential myoendothelial gap junction sites), strong punctate IKCa, Cx37 and Cx40 expression was present. SKCa, Cx37, Cx40 and Cx43 were localized to adjacent endothelial cell gap junctions. High-resolution immunohistochemistry demonstrated IKCa and Cx37-conjugated gold to myoendothelial gap junction-associated endothelial cell projections. Clear co-localization of KCa and Cxs suggests a causal relationship between their activity and the previously described differential functional activation of SKCa and IKCa. Such precise localizations may represent a selective target for control of vasodilator function and vascular tone.