Drug glucuronidation and hepatic lipid microsomal membrane profile in cholestatic rats followed paracetamol intoxication.

The uridin-diphosphoglucuronyl-transferase (UDP-GT) is a membrane-bound enzyme responsible for glucuronidation of endogenous and exogenous compounds. This work established the UDP-GT activity and its lipid membrane microenvironment in two experimental models: acute paracetamol intoxication, and cholestasis followed by acute paracetamol intoxication. Cholestasis was performed by bile duct ligation. After 7 days animals were injected with paracetamol (BDL-APAP group). Sham-operated rats were injected at day 7 with paracetamol (APAP group). Cholestatic and sham-operated rats injected with vehicle (BDL and control groups). UDP-GT activity was measured by a kinetic method for different substrates. Microsomal membrane phospholipid composition, cholesterol content and ultrastructure were determined. BDL-APAP group showed an increment in the UDP-GT activity except for chloramphenicol, morphine and paracetamol if compared to controls and to BDL group. The same increment was observed when BDL-APAP was compared to APAP except for chloramphenicol and lorazepam. Between BDL and APAP groups similar levels of activity were detected except for paracetamol. Microsomal phospholipid profile: phosphatidylcholine showed the lowest content in the BDL group, with a significant recovery in the BDL-APAP and APAP groups. Phosphatidylserine was markedly decreased in the APAP group compared to the rest and phosphatidylinositol was decreased in all the groups if compared to control values. An increment of phosphatidylethanolamine was seen in the APAP and BDL-APAP groups if compared to BDL and control values. A significant increment of microsomal cholesterol content was seen in BDL. Under these conditions, a different lipid microenvironment is produced, resulting in an increment of the enzyme activity for a variety of substrates. Copyright 1999 Academic Press.