Osmosignaling and volume regulation in intestinal epithelial cells.

Most cells have to perform their physiological functions under a variable osmotic stress, which, because of the relatively high permeability of the plasma membrane for water, may result in frequent alterations in cell size. Intestinal epithelial cells are especially prone to changes in cell volume because of their high capacity of salt and water transport and the high membrane expression of various nutrient transporters. Therefore, to avoid excessive shrinkage or swelling, enterocytes, like most cell types, have developed efficient mechanisms to maintain osmotic balance. This chapter reviews selected model systems that can be used to investigate cell volume regulation in intestinal epithelial cells, with emphasis on the regulatory volume decrease, and the methods available to study the compensatory redistribution of (organic) osmolytes. In addition, a brief summary is presented of the pathways involved in osmosensing and osmosignaling in the intestine.