title: Disposition of gemfibrozil and gemfibrozil acyl glucuronide in the rat isolated perfused liver.
abstract: Acyl glucuronides are reactive electrophilic metabolites and in vivo are readily hydrolyzed, undergo intramolecular rearrangement, and bind covalently to proteins. The isolated perfused liver preparation, using male Sprague-Dawley rats, was used to examine the hepatic disposition of the fibrate hypolipidemic agent gemfibrozil and its acyl glucuronide metabolite, 1-O-gemfibrozil-beta-D-glucuronide. Using a recirculating design, erythrocyte-free perfusion medium containing 1% (w/v) albumin was delivered to the liver via the portal vein at a flow rate of 30 ml/min, and for each experiment was spiked with either gemfibrozil (N = 4) or 1-O-gemfibrozil-beta-D-glucuronide (N = 4) at initial concentrations of 120 microM and 21 microM, respectively. In the gemfibrozil perfusions, the mean (SD) total perfusate clearance, half-life, hepatic extraction ratio of gemfibrozil, and the fraction of eliminated gemfibrozil excreted in bile as the glucuronide conjugate were 2.73 (0.30) ml/min, 76.9 (5.6) min, 0.091 (0.012), and 0.347 (0.154), respectively. In the 1-O-gemfibrozil-beta-D-glucuronide perfusions, the mean (SD) total perfusate clearance, half-life, hepatic extraction ratio, and fraction excreted in bile as the glucuronide conjugate were 19.5 (2.1) ml/min, 8.7 (0.9) min, 0.649 (0.068), and 0.534 (0.077), respectively. The higher hepatic extraction ratio for 1-O-gemfibrozil-beta-D-glucuronide could mostly be attributed to its higher unbound fraction in perfusate (0.182), compared with that of the parent drug (0.004), because the conjugate had a lower intrinsic clearance (305 ml/min) compared with the aglycone (751 ml/min). Control perfusions, conducted in the absence of a liver, showed negligible degradation of 1-O-gemfibrozil-beta-D-glucuronide over 90 min. However, in the presence of a liver, approximately 25% of 1-O-gemfibrozil-beta-D-glucuronide added to perfusate was hydrolyzed to gemfibrozil over 90 min. The study demonstrates the importance of the liver in the formation, uptake, hydrolysis, and excretion of 1-O-gemfibrozil-beta-D-glucuronide.
authors.affiliation: Department of Clinical Pharmacology, Queen Elizabeth Hospital, Woodville, South Australia.
authors.forename: B C
authors.initials: BC
authors.lastname: Sallustio
authors.forename: B A
authors.initials: BA
authors.lastname: Fairchild
authors.forename: K
authors.initials: K
authors.lastname: Shanahan
authors.forename: A M
authors.initials: AM
authors.lastname: Evans
authors.forename: R L
authors.initials: RL
authors.lastname: Nation
mesh_terms: D000818:Animals; D001646:Bile / Q000378:metabolism; D015248:Gemfibrozil / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D005965:Glucuronates / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D000960:Hypolipidemic Agents / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005965:Glucuronates; D000960:Hypolipidemic Agents; C094370:gemfibrozil 1-O-acylglucuronide; D015248:Gemfibrozil