Osmosensitive Taurine Release: Does Taurine Share the Same Efflux Pathway with Chloride and Other Amino Acid Osmolytes?

Swelling subsequent to hyposmotic conditions activates a process of volume regulation present in most cell types. This volume adjustment is accomplished by osmolyte translocation toward the extracellular space to reach a new osmotic equilibrium. Molecules involved in this homeostatic mechanism have been broadly classified into two categories: organic and inorganic osmolytes. Inorganic osmolytes comprise mainly the intracellular ions K+ and Cl–. Cell swelling–induced activation of separate K+ and Cl– channels has been described in most preparations. Organic osmolytes are grouped in three categories: amino acids, polyalcohols, and methylamines. These osmolytes, particularly taurine, are present in high intracellular concentrations and may also play a role as cytoprotectants.1 Amino acids are part of the organic osmolyte pool contributing to RVD in most cells.1,2 Among them, taurine has been studied in detail mainly because of its metabolic inertness, and it is often considered as representative of all osmolyte amino acids