A species comparison of 14C-labeled 7-ethoxycoumarin metabolism in precision-cut liver slices from guinea pig and dog using a phosphor imaging system.
The metabolism of 14C-labeled 7-ethoxycoumarin (7EC) has been investigated in precision-cut liver slices from guinea pigs and dogs. 7EC was incubated with slices in 12-well plates (4 slices/well; n = 3) for up to 8 hr. In addition, a new simple method was established for analyzing 7EC and its metabolites simultaneously by using thin-layer chromatography-radioluminography (TLC-RLG). In both species, 7EC was taken up rapidly into the slices and metabolized extensively under the conditions used (no serum fraction supplemented), showing both phase I and phase II metabolism. In guinea pig medium samples, 4-ethoxy-2-hydroxyphenylacetic acid (EHPA) and 7-hydroxycoumarin (7HC) glucuronide were major metabolites. In dogs, conjugated 7HCs (with D-glucuronic acid and sulfate) were major products but EHPA was formed only to a small extent. These results suggest that deethylation in dogs occurs to a much greater extent than in guinea pigs. These results demonstrate the advantages of precision-cut liver slices as a powerful tool to investigate the species specific metabolism of xenobiotics, since the conditions employed enabled both phase I and phase II reactions in vitro.
Terada
T
T
Pharmaceutical and Pharmacokinetic Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan.
Kaneko
H
H
Terashita
S
S
Tozuka
Z
Z
Tokuma
Y
Y
Hata
T
T
D000818:Animals; D002250:Carbon Radioisotopes; D003374:Coumarins / Q000378:metabolism*; D004285:Dogs; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D008297:Male; D013045:Species Specificity
D002250:Carbon Radioisotopes; D003374:Coumarins; C017299:7-ethoxycoumarin