Metaboism of Eicosapentaenoic Acid in the Liver of Rats : : Participation of the Peroxisomal β-Oxidation System in Chain-Shortening

抄録

Many studies on eicosapentaenoic acid (EPA) have confirmed its metabolic transformation to prostaglandins (PGs). However, it is not yet clear whether or not a large part of the EPA contained in foods is metabolized and degraded through some pathway other than transformation to PGs. The purpose of this study was to clarify whether the peroxisomal β-oxidation system participates in the chain-shortening of EPA.EPA-CoA in a reaction mixture for β-oxidation assay was incubated with liver peroxisomes obtained by sucrose density gradient centrifugation and the reaction products were analyzed by gas liquid chromatography. Metabolites having chain lengths reduced by 2 and 4 carbon units from EPA were detected. Furthermore, in order to examine the contribution of the peroxisomal and mitochondrial β-oxidation systems, the activities of purified fatty acyl-CoA oxidase and fatty acyl-CoA dehydrogenase toward EPA were determined and extrapolated to obtain the activities in the rat liver. The activities in the normal rat were 139 U/g liver for peroxisomal β-oxidation and 549 U/g liver for in mitochondrial β-oxidation. On treatment with diethylhexyphthalate (DEHP), a peroxisomal proliferator, the activities in the two organelles were induced to similar extents.From these findings it is concluded that hepatic peroxisomes participate in the chain-shortening of EPA together with mitochondria.