Cardiovascular Research Advance Access first published online on February 13, 2009
This version [Corrected Proof] published online on March 4, 2009
Cardiovascular Research, doi:10.1093/cvr/cvp060
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Prominent role of KCa3.1 in endothelium-derived hyperpolarizing factor-type dilations and conducted responses in the microcirculation in vivo
1 Department of Physiology, Universität zu Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
2 Department of Internal Medicine-Nephrology, Philipps-Universität, Marburg, Germany
* Corresponding author. Tel: +49 451 5004170; fax +49 451 5004171. E-mail address: dewit{at}uni-luebeck.de
Aims: The activation of endothelial Ca2+-dependent K+-channels, KCa3.1 (IKCa), and KCa2.3 (SKCa) has been proposed to be a prerequisite for endothelial hyperpolarization, which subsequently hyperpolarizes and relaxes smooth muscle [endothelium-derived hyperpolarizing factor (EDHF)-type dilation] and initiates conducted dilations. Although EDHF is the main mediator of acetylcholine (ACh)-induced dilation in the murine skeletal microcirculation, the differential contribution of KCa3.1 and KCa2.3 is not known.
Methods and results: We assessed agonist-induced and conducted dilations as well as endothelial hyperpolarization in the cremaster microcirculation of KCa3.1-deficient (KCa3.1–/–) and wild-type mice (wt) in vivo after blockade of NO and prostaglandins. Compared with wt, resting tone was enhanced by 
25% in arterioles of KCa3.1–/– mice. ACh-induced dilations in KCa3.1–/– mice were virtually abolished at low and intermediate concentrations and a remaining dilation at 10 µmol/L ACh was abrogated by blockade of KCa2.3 with UCL1684. Sodium nitroprusside- and adenosine-induced dilations were similar in wt and KCa3.1–/–. Focal application of ACh induced dilations at the local site in both genotypes, which conducted along the vessel. However, the amplitude of the dilation decreased with distance only in KCa3.1–/–. Blockade of KCa2.3 in wt did not affect conducted dilations. A KCa3.1 opener induced a conducting dilation in wt but not in KCa3.1–/–. Membrane potential recordings in vivo demonstrated endothelial hyperpolarization in response to ACh in both genotypes; however, the hyperpolarization was severely impaired in KCa3.1–/– (
membrane potential: –3 ± 1 vs. –14 ± 2 mV).
Conclusion: We conclude that KCa3.1 is of major importance for endothelial hyperpolarization and EDHF-type responses in skeletal muscle arterioles, and its deficiency is not compensated by KCa2.3. Sole activation of KCa3.1 is capable of initiating conducted responses, and KCa3.1 may contribute to the propagation of the signal, although its presence is not mandatory.
KEYWORDS Ca2+-dependent K+-channels; Conducted responses; Microcirculation
Time for primary review: 24 days
Present address. Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Australia.
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  C. de Wit Different pathways with distinct properties conduct dilations in the microcirculation in vivo Cardiovasc Res, October 31, 2009; (2009) cvp340v2. [Abstract] [Full Text] [PDF]
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