Relationship between malondialdehyde production and arachidonate consumption during NADPH-supported microsomal lipid peroxidation.

Fatty acid concentrations and malondialdehyde formation were determined before and during NADPH-supported lipid peroxidation in liver microsomes from rat, mouse, guinea pig and rabbit. In agreement with earlier reports, malondialdehyde production was greatest for rat, followed by mouse, and much less for guinea pig and rabbit. The microsomal content of total unsaturated fatty acids (18:1, 18:2, 18:3, 20:3, 20:4, 20:5, 22:5, 22:6) was approximately the same for rat and mouse and was lower in guinea pig and rabbit. Lipid peroxidation caused a time-dependent decrease in the polyunsaturated fatty acids, particularly 20:4 and 22:6, for all species. These decreases were most pronounced for rat and mouse. Alterations in the dietary regime for rat produced marked changes in microsomal fatty acid content as reported by others, and also caused changes in the rates of malondialdehyde production and polyunsaturated fatty acid consumption during lipid peroxidation. A comparison between the rates of malondialdehyde production and the rates of individual unsaturated fatty acid consumption was performed for each animal species and for rats fed different diets. A linear relationship was found between malondialdehyde production and 20:4 disappearance in individual microsomal preparations and in different species. A similar relationship was seen for the initial microsomal concentration of 20:4 and the initial rate of malondialdehyde formation. Other unsaturated fatty acids did not exhibit linear relationships. Various microsomal mixed-function oxidase variables were measured for the different species. No direct relationship between these values and malondialdehyde production was found.