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  • Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (K(Ca)) and connexins: possible relationship to vasodilator function?

Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (K(Ca)) and connexins: possible relationship to vasodilator function?

Journal of anatomy (2006-10-26)
Shaun L Sandow, Craig B Neylon, Mao X Chen, Christopher J Garland
ABSTRACT

Activation of endothelial cell small- (S) and intermediate- (I) conductance calcium-activated potassium channels (K(Ca)) and current or molecular transfer via myoendothelial gap junctions underlies endothelium-derived hyperpolarization leading to vasodilation. The mechanism underlying the K(Ca) 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, SK(Ca) and IK(Ca) 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 SK(Ca) and IK(Ca) 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 IK(Ca), Cx37 and Cx40 expression was present. SK(Ca), Cx37, Cx40 and Cx43 were localized to adjacent endothelial cell gap junctions. High-resolution immunohistochemistry demonstrated IK(Ca) and Cx37-conjugated gold to myoendothelial gap junction-associated endothelial cell projections. Clear co-localization of K(Ca) and Cxs suggests a causal relationship between their activity and the previously described differential functional activation of SK(Ca) and IK(Ca). Such precise localizations may represent a selective target for control of vasodilator function and vascular tone.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-von Willebrand Factor antibody produced in rabbit, IgG fraction of antiserum, buffered aqueous solution
Sigma-Aldrich
Anti-Connexin 43 Antibody, Chemicon®, from rabbit
Sigma-Aldrich
Anti-Potassium Channel KCa3.1 (Intermediate-conductance Ca2+-activated Potassium Channel 4) antibody produced in rabbit, affinity isolated antibody, lyophilized powder
Sigma-Aldrich
Anti-Potassium Channel KCa2.3, (C-term) (Small-conductance Ca2+-activated Potassium Channel 3) antibody produced in rabbit, affinity isolated antibody, lyophilized powder