8 Taurine

This chapter reviews the occurrence, distribution, metabolism, transport, and actions of the simple sulphur‐containing nonproteinaceous amino acid taurine. It is a ubiquitous constituent of virtually all animal cells, particularly enriched in the electrically excitable cells of the nervous system, retina, heart, and muscles. Taurine is present in both neuronal and glial cells, exhibiting moderate regional and cellular variations. It is partly synthesized in situ, but the main supply to the central nervous system (CNS) is from blood plasma. Taurine is taken up by the brain via a saturable transporter and penetrates cells requiring Naþ and Cl . The release is fomented by cell swelling, depolarizing stimuli, and various cell‐ damaging conditions. Taurine interferes with both GABAA and glycine receptors, depending on their subunit composition and amino acid structure. It also affects GABAB receptors, at least in specific structures. The existence of specific taurine receptors and the function of taurine as a neurotransmitter await further investigation. A number of taurine derivatives have been synthesized and tested for their efficacy in counteracting seizures, ameliorating ischemia‐induced damage, and protecting neural cells from the toxic actions of xenobiotics. This is an area of research, which may produce new drugs and therapeutic strategies in the future. List of Abbreviations: AMPA, ( )‐2‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate; cGMP, cyclic GMP; CNS, central nervous system; CPP, 3‐[( )‐2‐carboxypiperazin‐4‐yl]propyl‐1‐phosphonate; CSF, cerebrospinal fluid; DIDS, diisothiocyanostilbene‐2,20‐disulfonate; DOPAC, dihydroxyphenylacetic acid; GABA, g‐aminobutyric acid; GES, guanidinoethanesulfonate; LLP‐TAU, taurine‐induced long‐lasting potentiation; L‐NAME,N‐nitro‐L‐arginine methylester hydrochloride; MPPþ, 1‐methyl‐4‐phenylpyridinium; PKA, protein kinase A; PKC, protein kinase C; SITS, 4‐acetamido‐40‐isothiocyanostilbene‐2,20‐disulfonate; TAG, taurine antagonist; TUG1, taurine‐upregulated gene 1