Comparative metabolism of DDAO benzoate in liver microsomes from various species.

DDAB (6,8-dichloro-9,9-dimethyl-7-oxo-7,9-dihydroacridin-2-yl benzoate) is a newly developed near-infrared fluorescent probe for human carboxylesterase 2 (hCE2), exhibiting high specificity and good reactivity for real-time monitoring the enzymatic activities of hCE2 in complex biological systems. In order to explore the applicability of DDAB in commonly used animal species, the interspecies difference in DDAB hydrolysis was carefully investigated by using liver microsomes from human and five experimental animals including mouse, rat, dog, minipig and monkey. Metabolite profiling demonstrated that DDAB hydrolysis could be catalyzed by all tested liver microsomes from different animals but displayed significant difference in the reaction rate. Chemical inhibition assays demonstrated that carboxylesterases (CEs) were the major enzymes involved in DDAB hydrolysis in all tested liver microsomes, indicating that DDAB was a selective substrate of CEs in a variety of mammals. However, the differential effects of loperamide (LPA, a specific inhibitor against hCE2) on DDAB hydrolysis among various species were observed. The apparent kinetic parameters and the maximum intrinsic clearances (CLmax) for DDAB hydrolysis in liver microsomes from different animals were determined, and the order of CLmax values for the formation of DDAO was CyLM>MLM≈PLM>RLM>HLM≈DLM. These findings were helpful for the rational use of DDAB as an imaging tool for CE2 in different mammals, as well as for translational researches on the function of mammalian CEs and CE2-associated drug-drug interactions.

[Expression of CYP3A29 mRNA in Chinese experimental miniature pig's livers quantitated with real-time reverse transcription polymerase chain reaction].

CYP3A29 is the most important key enzyme for drug metabolism in pig's liver. Research of the characters of CYP3A29 mRNA expression in Chinese experimental miniature pig's livers is significant for evaluating it whether suitable for experimental model for drug metabolism mediated by human CYP3A4 enzyme. In this study, the levels of CYP3A29 mRNA expression in livers of Bama miniature pigs, Guizhou miniature pigs and Rongchang pigs were studied by TaqMan-mediated quantitative RT-PCR. Results indicated that the CYP3A29 mRNA expression levels in livers of these species were close to literatures of human. Levels of CYP3A29 mRNA expression were similar among livers of Bama miniature pigs, Guizhou miniature pigs and Rongchang pigs, but interindividual variations were quite large. It was suggested that Bama miniature pigs and Guizhou miniature pigs were both feasible for experimental animal model for evaluating drug metabolism in some degree.