The biosynthesis of taurine from N-acetyl-L-cysteine and other precursors in vivo and in rat hepatocytes

The synthesis of taurine from N-acetylcysteine has been examined in rats in vivo and in rat hepatocyte suspensions in vitro. In rats in vivo, administration of N-acetylcysteine significantly increased urinary taurine (3 fold) 24h after dosing and liver glutathione levels. Liver taurine was not increased significantly. In hepatocytes incubated in the presence of N-acetylcysteine, glutathione concentration increased to a maximum after 1 hour but the increase was not dependent on the concentration of N-acetylcysteine. In contrast, after an initial lag phase, taurine synthesis increased in relation to the concentration of N-acetylcysteine and continued for 3 hours. Glutathione synthesis seems to be preferential to taurine synthesis. Taurine synthesis from cysteine sulphinate was greater and from hypotaurine was greatest and maximal after 1 hour. Implications for the mechanism of protection by N-acetylcysteine are discussed.