Purpose: To Study the possible mechanisms of change of thiosulfate sulfurtransferase (TST) activity in cholestatic rat liver and serum.
Methods: Rats were divided into seven groups: those receiving a sham operation (Sham group), with a bile duct obstruction (BDO) alone (BDO group), with a BDO plus taurocholic acid (TCA) injection (BDO plus TCA group), with a BDO plus tauroursodeoxycholic acid (TUDCA) injection (BDO plus TUOCA group), a choledocho-caval shunt (CCS) operation (CCS groups), a CCS operation plus TCA injection (CCS plus TCA group) and a CCS operation plus TUDCA injection (CCS plus TUOCA group). The TST activities in the serum and in the hepatic subcellular fractions isolated from above experimental rats were determined. The K_(m) and V_(max) values of this hepatic enzyme were measured.
Results: The liver cytosolic, mitochondrial and microsomal TSTs activities, as well as the TST V_(max) values were found to be significantly decreased in the BDO plus TCA and BDO groups compared to the control group. The activity and V_(max) value of the liver cytosolic TST were also found to be significantly decreased in the CCS plus TCA group. Conversely, there was no variation in the K_(m) values of the hepatic enzymes in any of the above experimental groups. The serum TST activities in the CCS plus TCA and BDO plus TCA groups, were significantly increased compared with the control, CCS and BDO groups. However, the serum and hepatic enzyme activities were unchanged in both the CCS plus TUDCA and BDO plus TUOCA groups.
Conclusion: The above results indicate that TCA represses the biosynthesis of TST in the liver. Also, the elevated TST activity in the serum is most likely due to an increase in the permeability of hepatocytes membrane upon TCA mediated liver cell necrosis.
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