O 2−dependent lipid peroxidation does not affect the molecular order in hepatoma microsomes

Microsomal membranes from rat liver and from the fast-growing Morris hepatoma 3942A have been peroxidized to different extents and the order parameter of the membranes measured by fluorescence depolarization of the probe 1,6-diphenyl-1,3,5-hexatriene. The data have been analysed by applying a mathematical approach that takes into account simultaneously static and dynamic fluorescence parameters. It appears that tumour membranes are more ordered than the control and their order parameter does not increase with greater exposure to the action of O −2radicals in contrast to liver membranes. The fatty acid composition of the membrane lipids has been studied under different experimental conditions and correlated to the behaviour of the physical parameter.