Abstract
Species differences and substrate specificities of liver aldehyde oxidase were examined in several mammalian species using methotrexate (MTX), benzaldehyde (BA), phthalazine (PH) and N1-methylnicotinamide (NINA) as a substrate. Significant species differences were observed when aldehyde oxidase activities were examined in rabbits, guinea pigs, hamsters, monkeys and dogs. Monkey had the highest activities using BA or PH as a substrate, and rabbits showed a significant oxidase activity toward MTX. Five strains of rats (Slc:Wistar/ST, Sea:SD, Jcl:SD, S1c:SD and WKA/Sea) demonstrated marked strain differences. Substrate specificities, Km values and immunoblot analysis indicated that the strain differences were due to the amounts of AO. Human liver cytosols exhibited relatively high aldehyde oxidase activities, but they were individually different. The existence of AO isozymes in human was suggested from the immunoblot analysis.
