ASSAY OF ALDEHYDES FROM LIPID-PEROXIDATION - GAS-CHROMATOGRAPHY MASS-SPECTROMETRY COMPARED TO THIOBARBITURIC ACID

The oxidation of lipids, lipid peroxidation, is usually assayed with t hiobarbituric acid (TEA). We compare the TEA assay measuring TEA-react ive substances (TEARS), and a new gas chromatography-mass spectrometri c (GC-MS) assay measuring malondialdehyde (MDA) with unsaturated fatty acids and biological samples. The extent of oxidation to different un saturated fatty acids is related to the total number of bis-allylic po sitions, the position of the first double bond from the methyl terminu s, and the lipid chain length. The extent of oxidation of different bi ological samples or organs is related to the component polyunsaturated fatty acids. Both the GC-MS and TEA assays give parallel results for oxidation of unsaturated fatty acids and biological samples. The GC-WS assay is about two-to sixfold more sensitive than the TEA assay for o xidation of unsaturated fatty acids. In contrast, the TEA assay gives about two- to sixfold higher TEARS than MDA by GC-MS assay in biologic al samples, possibly due to the nonspecificity and artifactual formati on of derivatives in the acid-heating step of the TEA assay. The GC-MS assay is shown to be useful in oxidation-related cell culture studies with as few as 250,000 neural cells. These results suggest that the G C-MS assay is a useful, sensitive, and specific assay for lipid peroxi dation. The TEA assay is also quite useful because of its sensitivity and simplicity, if one clearly understands its nonspecificity. (C) 199 7 Academic Press.