Distribution of Fatty Acid Ethyl Esters in Long Evans Rats Following Acute Ethanol Ingestion

Abstract

Summary: Fatty acid ethyl esters (FAEEs) are members of a class of nonoxidative metabolites of ethanol. These lipophilic moieties have been detected in various animal and human tissues in vivo and in vitro. A one-step liquid-liquid extraction method with subsequent analysis by GC/MS is described for the identification and quantitation of palmitic acid ethyl ester and stearic acid ethyl ester in blood, liver, and brain from Long Evans rats administered ethanol by feeding needle. Animals received one of four doses of ethanol (1, 2, 4, and 5 g/kg) as a 25% w/v gavage solution. Control animals received tap water. One hour after gavage, a blood specimen (3-5 mL) was collected by cardiac puncture and the animals were euthanized in accordance with guidelines promulagated by the Institutional Animal Care and Utilization committee. Necropsies included the complete resection of liver and removal of whole brain. Blood ethanol concentrations (BECs) were determined by GC headspace with n-propanol as internal standard. Heptadecanoic acid ethyl ester was added as internal standard to 1.0 mL aliquots of blood or 2 g liver or whole brain homogenates and extracted in toluene-hexane (1:1) at pH 5. Extraction mixtures were throroughly mixed and centrifuged. Solvent layers were removed and evaporated to dryness under nitrogen. Reconstituted residues were injected into a GC/MS equipped with an HP INNOWax GC column. Selected ions in the SIM mode included 88, 101, and 157. BEC data and FAEE concentrations for blood, liver, and brain are reported. These results suggest that a one-step extraction method coupled with GC/MS analysis could be used in identifying and quantitating nonoxidative fatty acid ethyl ester metabolites of ethanol in vivo.

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• [K]Key [K]Words: Ethanol, Fatty Acid Ethyl Esters, Gc/MS