Fluorospectroscopic analysis of the fluorescent substances in peroxidized microsomes of rat liver.

The fluorescent substances formed in rat liver microsomes in the course of lipid peroxidation were investigated by fluorescence techniques. The fluorescence emitted from peroxidizing microsomes continuously increased as lipid peroxidation progressed, while the steady-state fluorescence anisotropy increased and then reached a plateau. A similar increase was observed in the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene in peroxidizing microsomes. The fluorescence from peroxidized microsomes consisted of at least three species having short, middle or long fluorescence lifetimes. The lifetimes and relative amplitudes of fluorescence were unaffected by the extent of lipid peroxidation. Both fluorescence of the chromolipids extracted and the proteins isolated from peroxidized microsomes had the same characteristics in fluorescence lifetimes as the fluorescence from whole peroxidized microsomes. Thus, these lipids and proteins appear to be the major biological substances responsible for the fluorescence emanating from whole peroxidized microsomes. Furthermore, fluorescent substances formed in microsomes seem to increase in quantity rather than change in quality as lipid peroxidation progresses.