The protective effect of cysteine on chemical-induced liver injury in rats.

The possible protective effect of cysteine on chemical-induced liver injury was studied in rats in vivo and in vitro. There was no increase in the activity of serum glutamic oxaloacetic transaminase (GOT) of rats pretreated with cysteine (1.2 g/kg, p,o.) followed by 0.25 ml/kg carbon tetrachloride (CCl4), d-galactosamine (GalN) or alpha-naphthylisothiocyanate (ANIT). However, rats pretreated with cysteine followed by 0.5 ml/kg CCl4 were not protected. The content of cytochrome P-450, activity of aminopyrine N-demethylase or serum ratio of 5,5-dimethyl-2,4-oxazolidinedione (DMO) to trimethadione (TMO) (DMO/TMO ratio) after CCl4, GalN or ANIT were not altered by pretreatment with cysteine. However, pretreatment with cysteine prevented changes in the content of cytochrome P-450, activity of aminopyrine N-demethylase and DMO/TMO ratio in serum as well as the activities of serum GOT and GPT when the rats were treated with bromobenzene (BZ). The degree of lipid peroxidation from CCl4 was markedly reduced by the presence of 10(-4)M cysteine. These results suggest that cysteine has a protective effect on chemical-induced liver injury produced via epoxide metabolites.