FIGURE 3. Intermediate conductance calcium-activated potassium channels in endothelial cells.


Intermediate conductance calcium-activated potassium channels in endothelial cells. (A) The various configurations of the patch clamp technique are shown. The patch-clamp technique is an electrophysiological technique that allows the study of ionic channels expressed in the cell membrane or in a lipid bilayer. A polished glass pipette is brought into contact with a given cell. When the tip of the pipette touches the cell membrane, a tight seal is formed (giga-seal). Then, by applying various maneuvers, suction, excision, permeation of the membrane with toxins, the global electrophysiological properties of the ionic channel expressed by the cell and/or the properties of individual channels can be studied. (B) IKCa in freshly dissociated porcine coronary endothelial cells (outside-out configuration of the patch-clamp technique). Single-channel activity was recorded at the indicated holding potentials under asymmetrical K+ gradients with Ca2+ fixed at 250 nM in the pipette solution. Mean unitary currents were plotted against holding potential, fitted with a linear function and the slope conductance computed (17.5 pS). (C) The effects of iberiotoxin and the subsequent addition of charybdotoxin were recorded. Distributions of unitary conductance amplitude (recorded at 0 mV and using 250 nM free Ca2+ in the pipette solution) are shown, together with representative traces. A Gaussian fit was performed for every single channel experiment, and the amplitude of single channels was determined with the best fit. Then, the mean of the obtained amplitudes was calculated. These data show that the current is insensitive to iberiotoxin (IbTX) but blocked by charybdotoxin (ChTX).

From: Chapter 1, Endothelium-Dependent Hyperpolarizations: The Classical “EDHF” Pathway

Cover of The Endothelium
The Endothelium: Part 2: EDHF-Mediated Responses “The Classical Pathway”.
Félétou M.
Copyright © 2011 by Morgan & Claypool Life Sciences Publisher.

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