4-Hydroxy-2-nonenal (HNE), an aldehyde end product of lipid peroxidation in biological systems, is capable of producing a range of powerful biological effects. Despite its biological relevance, the metabolic fate of this aldehyde is unknown in vivo. This study examines the urinary excretion of HNE in the rat and the nature of metabolites formed. Following iv administration of [3H]HNE, the majority of the dose appeared in urine (67.1% after 48 h). The radio-HPLC metabolic profile showed that no unchanged parent compound was detected in urine whereas at least four metabolites were present, most of them corresponding to mercapturic acid conjugates. Two major pathways were involved in the biotransformation of HNE in vivo: (i) reduction/oxidation of the aldehyde group, and (ii) conjugation to endogenous glutathione leading to mercapturic acid conjugates in urine. These end products were isolated by HPLC and identified by mass spectrometry as HNE mercapturic acid, 1,4-dihydroxynonene mercapturic acid, 4-hydroxynonenoic mercapturic acid, and the corresponding lactone.

SUMMARY4-Hydroxy-2(E)-nonen-1 -al-diethylacetal 9 (HNE-DEA) was prepared by condensation of the Grignard compound derived from propiolaldehyde diethylacetal and nhexanal followed by reduction of the resulting 4-hydroxy-2-nonyn-1-al-diethylacetal 2 with LiAIH4 according to the literature procedure with minor modifications. Swern oxidation[3H]NaBH4 and I2H]NaBH4 reduction of 5. gave rise respectively to (4-3H]HNE-DEA (specific activity 222 GBq/mrnol) and [4-*H]HNE-DEA.KEY WORDS: Lipid peroxidation product: 4-Hydroxy-2-nonena1, 4-Hydroxy-2(E)-The free radicals generated in biological systems play an important role in causing oxidative damage to living cells, particularly to the biornembranes. Among many compounds, 4-hydroxy a$-unsaturated aldehydes (hydroxy alkenals) are formed as degradation