Abstract
Ethoxycoumarin (EC) and tolbutamide (TOL) were selected as examples of high- and low-clearance drugs, respectively, to investigate suitable methodologies for obtaining kinetic data on metabolism by precision-cut rat liver slices. A number of characteristics of the slice incubation were compound-dependent. TOL showed linear rates of metabolism over a longer time period than EC and was insensitive to the method of incubation (rotating vials and gyrating culture plates). Also, the need for complete tissue disruption (e.g. via sonication) before analysis was essential for EC but unimportant for TOL. This may suggest that conjugates do not freely diffuse out of the liver slice unlike oxidative metabolites. Both drugs showed rates of metabolism that were dependent on slice thickness (150-530 microns). A high turnover (intrinsic clearance 7.9 microliters/min) and low KM (1.3 microM) for EC, and a low turnover (intrinsic clearance 0.8 microliter/min) and high KM (707 microM) for TOL were determined in slices. These differences in kinetic behavior are comparable with those seen in hepatic microsomes, freshly isolated hepatocytes, and in vivo.
Log in using your username and password
Pay Per Article - You may access this article (from the computer you are currently using) for 1 day for US$35.00
Regain Access - You can regain access to a recent Pay per Article purchase if your access period has not yet expired.
In this issue
Kinetics of drug metabolism in rat liver slices. Rates of oxidation of ethoxycoumarin and tolbutamide, examples of high- and low-clearance compounds.
