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(Hypertension. 2008;52:470.)
© 2008 American Heart Association, Inc.

Editorial Commentaries

Vanishing Act

Protein Kinase C–Dependent Internalization of Adenosine 5'-Triphosphate–Sensitive K⁺ Channels

William F. Jackson

From the Department of Pharmacology and Toxicology, Michigan State University, East Lansing.

Correspondence to William F. Jackson, Pharmacology and Toxicology, Michigan State University, B-420 Life Sciences Building, East Lansing, MI 48824. E-mail jacks783@msu.edu

An extract of the first 250 words of the full text is provided, because this article has no abstract.

Potassium channels play an important role in the regulation of vascular smooth muscle tone and, thus, contribute to the regulation of blood pressure, blood flow, and microvascular exchange.¹ These channels importantly participate in the determination of vascular smooth muscle cell (VSMC) membrane potential,^1,2 which, in turn, controls Ca²⁺ influx through voltage-gated Ca²⁺ channels^1,2 and has been implicated in the control of Ca²⁺ release and Ca²⁺ sensitivity of VSMCs.¹ VSMCs express a diverse array of K⁺ channels that contribute to the regulation of VSMC function,¹ including 1 type of vascular ATP-sensitive K⁺ (K_ATP) channels.^2,3

K_ATP channels consist of a tetramer of -pore–forming subunits from the KIR6.X family of inwardly rectifying K⁺ channels, along with complimentary sulfonylurea receptor (SUR) subunits that are members of the ATP-binding cassette family of proteins.² The SUR subunits are essential for normal trafficking of K_ATP channels, modulate channel function, and are the binding sites for sulfonylurea antagonists of these channels, such as glibenclamide.² Vascular smooth muscle K_ATP channels appear to be composed of KIR6.1 and SUR2B subunits,² although some VSMCs may also express K_ATP channels composed of KIR6.2/SUR2B.³

As originally described, K_ATP channels open during hypoxia or ischemic conditions when cellular ATP levels fall, decreasing cell excitability and protecting energy-limited cells.² However, both in vitro and in vivo studies suggest that VSMC K_ATP channels may be open under resting conditions and contribute to the regulation of VSMC membrane potential and vascular tone.^1,2 Importantly, the activity of K_ATP channels can be modulated by a number of physiologically . . . [Full Text of this Article]

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