Signalling mechanisms involved in volume regulation of intestinal epithelial cells

Most mammalian cells have developed compensatory mechanisms to respond to t he variable osmotic stress caused by changes in the concentrations of intra cellular osmo-active substances (e.g. glucose, amino acids, lactate) or by variations in the osmolarity of the surrounding medium. In response to osmo tic cell swelling, the Regulatory Volume Decrease (RVD) is triggered and di rects a reduction in the tonicity of the cell by the concerted opening of c ation and anion selective ion channels. To date, the K+ and Cl- conductance s activated upon hypo-osmotic stimulation have been characterised electroph ysiologically in many different cell systems. The molecular identity of the channels however, as well as the mechanism(s) involved in their activation have not yet been fully clarified and may differ between cell types. In th is review, we will evaluate the different signalling pathways activated by osmotic cell swelling and discuss their putative role(s) in ion channel reg ulation, in maintaining cellular volume homeostasis, and in auto- and parac rinic signal transduction, with emphasis on intestinal epithelial cells. Co pyright (C) 2000 S. Karger AG, Basel.