Peroxidation of common W-6 PUFAs such as linoleic acid DGLA and arachidonic acid can give rise to 4-HNE 4-HNE is cleared rapidly from the plasma and undergoes enterohepatic circulation as a glutathione conjugate in the rat 7334 About two thirds of an administered dose of 4-HNE is excreted within 48 hours in the urine primarily in the form of mercapturic acid conjugates 8626 The C-1 aldehyde of 4-HNE is reduced to an alcohol in about half of these metabolites The remainder are C-1 aldehydes or have been oxidized to C-1 carboxylic acids These aldehydes and carboxylic acids can also form Y-lactols and Y-lactones respectively producing at least 4 or 5 end urinary metabolites of 4-HNE in vivo