Organic osmolyte channels in cell volume regulation in vertebrates

Volume-activated organic osmolyte channels are found in a variety of verteb rates and cell types and show both common and disparate features. Upon expo sure to hypotonic conditions, organic compounds such as taurine are release d through these channels, reducing the intracellular solute concentration a nd thereby restoring cell volume. Various structurally diverse membrane pro teins have been proposed as the channel. Accumulating evidence suggests tha t some of these proteins may play a more significant role as regulators tha n as the channel itself. Intracellular ionic strength may also modulate the release of organic osmolytes through these channels. (C) 1999 Wiley-Liss, Inc.