Strain and sex differences in drug hydrolase activities in rodent livers

Carboxylesterase (CES) 1, CES2, and arylacetamide deacetylase (AADAC) are the major drug hydrolases in humans, and they have different substrate preferences. Because rodents are widely used in preclinical studies, we aimed to clarify the extent of the species, strain, and sex differences in hydrolase activity in rats and mice. Hydrolase activities for 24 compounds were evaluated in Fischer 344, Sprague-Dawley, and Wistar-Imamichi rat liver microsomes (RLM) and Balb/c, C3H/He, C57BL/6J, and ddY mouse liver microsomes (MLM) by comparing the results with the activities in human liver microsomes (HLM). Imidapril hydrolase activities in RLM from all strains were substantially higher than those in MLM and HLM, whereas oseltamivir was hardly hydrolyzed in rodents, although both are specific substrates of CES1 in humans. In rats, males tended to show higher hydrolase activities for most human CES1 substrates than females. Hydrolase activities for irinotecan and procaine, which are CES2 substrates in humans, tended to be higher in RLM and MLM than in HLM. Rifamycins, substrates of human AADAC, were not hydrolyzed in RLM and MLM. The results of this study provide important information about the species, strain, and sex differences in hydrolase activities in rats and mice.