Induction of Rat Liver gamma-Glutamyl Transpeptidase by Bile Acid Load

Kim, Sung Kook; Kim, You Hee

Abstract

BACKGROUND/AIMS
In order to elucidate the possible mechanism of increase of y-glutamyl transpeptidase (y-GTP) activity in cholestatic liver and serum was studied. METHOD: Rats were divided into eight groups: Normal, sham operated control, bile duct obstruction (BDO) alone (BDO group), BDO plus taurocholic acid (TCA) injection (BDO plus TCA group), BDO plus tauroursodeoxycholic acid (TUDCA) injection (BDO plus TUDCA group), choledoco-caval shunt (CCS) operation (CCS groups), CCS plus TCA injection (CCS plus TCA group), and CCS plus TUDCA injection (CCS plus TUDCA group). Y-GTP activity was determined in the serum and liver cytosolic, mitochondrial and microsomal preparations isolated from above experimental rats. The values of Km and Vmax in this hepatic enzyme was measured. RESULT: the activities of liver cytosolic and microsomal y-GTP showed a significant increase in the CCS group. The activities of liver cytosolic, mitochondrial and microsomal y-GTP showed a significant increase in the BDO group. And the activity of serum y-GTP showed a marked increase in teth CCS and BDO poups. However, y-GTP activities in the serum and in liver microsomal prepatation rose more rapidly in the BDO group tban CCS. Y-GTP activity in liver cytosolic and microsomal preparatians, and its Vmax value incmmxl significantly in both CCS plus TCA group, and BDO plus TCA group than each control group, such as CCS and BDO group. On the other hand, the values of Km of the hepatic subcellular y-GTP did not change in the all experimental groups. Sennn y-GTP activity increased significantly in both CCS plus 7CA group, and BDO plus TCA group than each control group. However, these serum and hepatic enzyme activities did not change in both CCS plus TUDCA group and BDO plus TUDCA group.
CONCLUSIONS
The above results suggest that 7CA stimulates biosynthesis of the y-GTP in the liver. And the elevations of the serum enzymes activity thought to be caused by increase of hepatocyte membrane permeability by a physical property (detergency) of TCA, which cause the enzyme to leak into the blood in large quantities.