The volume-regulated anion channel, VRAC, plays an important role in cell volume regulation. This channel is permeable for a wide variety of anions, amino acids, and organic osmolytes, including taurine. However, nothing is known about possible water permeability of this channel. Water permeability of endothelial cells is estimated from the initial rate of cell swelling because of a hypotonic challenge. As a result of simultaneous volume and current measurements, it will be shown that water permeability is decreased by inhibition of VRAC. It is concluded that water permeates VRAC and might be able to accelerate water transport by providing an additional permeation pathway for water. Therefore VRAC can be considered as a water-permeable, "wet" channel.
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