Homocystein  (Hcy),one of the thio-amino acid is known as a risk   factor in some cardiovascular diseases with releasing O₂ radical . It has also been reported that; there is oxidative stress effects of Hcy in cholestasis. The aim of this study is to determine plasma Hcy alteration and nitric oxide (NO) in liver and its
   effects on pathologic disfunction.

            In this study , 150 Spraque – Dawley male rats with 200 ± 20g body weight were used in the experiments and they were randomly divided in three control, SHAM and bile duct ligation (BDL) groups (n= 10-12) . In 7^th,14^th,21^st and 28^th days cholestasis was observed in BDL group,the animal were anesthetized with ether
   and then blood samples were taken from heart directly and analysed for cystein , methionine by HPLC and HPLC-UV. Two hours before blood sampling , 40 and 100 mg/kg methionine were injected (I.P) .

All data are expressed as mean ± SEM. Statistical evaluation of data performed by SPSS soft ware using analysis of variance (ANOVA) followed by post hoc test. P-values less than 0.05 were considered statistically significant .

The results suggest that billirubin and hepatic enzymes were significantly elevated in BDL rats compared with SHAM and controls (P<0.05). Homocystein concentration was significantly rised in 14^th day in BDL group (P<0.05). The plasma cystein and methionine level were significantly elevated in BDL rats compared with SHAM and control groups ( p = 0.01) . Plasma nitrate / nitrite ratio were significantly increased in BDL rats compared with SHAM and control rats (P<0.05). With these data we suppose that some of the systemic oxidative stresses in BDL rat model of   cholestasis contributes possibly through NO-dependent mechanisms disorders.