ABSTRACT
This chapter focuses on the rapid cell volume regulatory responses that are mediated by uptake or loss of inorganic ions in two renal medullary nephron segments, mouse medullary thick ascending limb of Henle and rat inner medullary collecting duct. The maintenance of cell volume is one of the fundamental properties of all animal cells, including renal epithelial cells. Since the mouse medullary ascending limb of Henle will be used as a model epithelium for discussion of volume-regulatory responses in the kidney, it is important to review our current understanding of the membrane transport properties of this nephron segment. The ability of kidney epithelia to transport solutes and water requires that apical and basolateral membranes of these cells form distinct structural and functional domains. Cell shrinkage may occur with a sudden decrease in cell net solute entry or with exposure of cells to an absolute or relative increase in extracellular osmolality.
