Cysteine sulfinate decarboxylase and cysteine dioxygenase activities do not correlate with strain-specific changes in hepatic and cerebellar taurine content in aged rats

Taurine is a free sulfur-containing amino acid that is found in abundance in mammalian tissues and fluids. Many biological roles have been proposed for this amino acid, including reducing oxidative stress and cytotoxicity. Taurine has previously been reported to decline in tissues during aging which could exacerbate an age-related increase in oxidative stress. The aim of the present study was to elucidate the mechanism responsible for the observed decline in tissue taurine content. We measured the activity of the major taurine biosynthetic enzymes, cysteine sulfinate decarboxylase and cysteine dioxygenase, in liver and cerebellar tissues of rats. Tissues from male adult and aged Fischer 344 (F344; 10 and 28 months), Sprague-Dawley (SD; 5, 20 and 25 months), and F344/Brown-Norway hybrid (FBNF1; 14 and 33.5 months) rats were used. We observed a significant decline in hepatic taurine content of the F344 animals but the decline in the liver of SD and FBNF1 animals was non-significant. Hepatic cysteine sulfinate decarboxylase and cysteine dioxygenase activities were significantly lower in aged F344 rats but not in the other strains. Cerebellar taurine content was significantly lower in aged F344 and SD rats without a concomitant decline in cysteine sulfinate decarboxylase activity. These results suggest that a decline in hepatic de novo taurine biosynthesis might be partially responsible for a reduction in tissue taurine content in F344 rats. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.