A fluorescence method for the determination of plasma susceptibility to lipid peroxidation

Objective: We propose a fluorescence kinetics method for monitoring plasma susceptibility to peroxidation. Design and Method: Plasmatic peroxidation was induced by CuSO4 (500 mu M), and fluorescence was measured every 30 min. Kinetics were represented by a sigmoidal curve from which it was possible to calculate the latency time (lag-time) and the propagation velocity (slope) of plasma peroxidation. Results: The lag-time monitored by the fluorescence kinetics method corresponded to the formation of thiobarbituric acid reactive substances, and to progressive depletion of polyunsaturated fatty acids and alpha-tocopherol. The mechanism of reaction appeared to be dependent upon plasmatic hydroperoxides, and independent of oxygen radicals. Plasma storage is possible for at least two months at -80 degrees C, and reproducibility of the method is very good. Conclusions: Fluorescence kinetics provide a highly comprehensive picture of plasma susceptibility to peroxidation in comparison with the conventional measurements of anti- and prooxidant ratios. Copyright (C) 1999 The Canadian Society of Clinical Chemists.