CELL-VOLUME REGULATED TRANSPORTERS OF COMPATIBLE OSMOLYTES

Virtually all cells respond to hypertonicity by accumulating certain s mall organic solutes (compatible osmolytes) that, in contrast to intra cellular ions, do not perturb macromolecular function. Several importa nt compatible osmolytes are accumulated by coupled transport. Transcri ption of genes encoding these cotransporters is increased by hypertoni city and a tonicity-responsive enhancer element has been identified. W hen cells return to an iso-osmotic environment, osmolytes are rapidly lost through a pathway that current evidence indicates may be a volume -sensitive chloride channel.