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      Multiple Types of Chloride Channels in Bovine Pulmonary Artery Endothelial Cells

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          We have characterized two different types of Cl<sup>–</sup> currents in calf pulmonary artery endothelial (CPAE) cells by using a combined patch-clamp and Fura-2 microfluorescence technique to measure simultaneously ionic currents and the intracellular Ca<sup>2+</sup> concentration, [Ca<sup>2+</sup>]<sub>i</sub>. Exposure of CPAE cells to 28% hypotonic solution induces cell swelling without a change in membrane capacitance and [Ca<sup>2+</sup>]<sub>i</sub>, and concomitantly activates a current. This current, I<sub>Cl</sub>, <sub>vol</sub>, is closely correlated with the changes in cell volume and shows a modest outward rectification. It slowly inactivates at potentials more positive than +60 mV but is time- and voltage-independent at other potentials. Increase in [Ca<sup>2+</sup>]<sub>i</sub> by different maneuvers, such as application of vasoactive agonists (ATP), ionomycin, or loading of the cells directly with Ca<sup>2+</sup> also activates a Cl<sup>–</sup> current, I<sub>cl</sub><sub>ca</sub>· This current slowly activates at positive potentials, inactivates quickly at negative potentials and shows strong outward rectification. A time-independent component of the current activated by elevation of [Ca<sup>2+</sup>]<sub>i</sub> alone can be inhibited by cell shrinking by exposing the cells to hypertonic solution, indicating that an increase in [Ca<sup>2+</sup>]<sub>i</sub> also co-activates I<sub>Clvol</sub>· Forskolin or cAMP never activated a current in CPAE cells, which indicates the lack of cAMP-activated channels in these cells. There is also no evidence for the existence of voltage-gated C<sup>-</sup> channels in resting, nonstimulated cells. Challenging a cell with elevated [Ca<sup>2+</sup>]<sub>i</sub> and hypotonic solutions activated I<sub>Clvol</sub> on top of I<sub>Cl</sub><sub>ca</sub>, suggesting that I<sub>Cl Ca</sub> and I<sub>Clvol</sub> are different channels. We conclude that CPAE cells do not express voltage-gated (CIC-type) or cAMP-gated (CFTR-type) Cl<sup>-</sup> channels, but activate large Cl<sup>-</sup> currents after volume (mechanical?) or chemical (Ca<sup>2+</sup>) stimulation.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          24 September 2008
          : 34
          : 3
          : 220-228
          KU Leuven, Laboratorium voor Fysiologie, Campus Gasthuisberg, Leuven, Belgium
          159226 J Vasc Res 1997;34:220–228
          © 1997 S. Karger AG, Basel

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          Page count
          Pages: 9


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