Selective sensitization of chemiluminescence resulted from lipid and oxygen radical reactions

Eu3+-tetracycline complex (EuT) increased the chemiluminescence (CL) intensity of linolenic acid micells (UFA-somes) oxidized with lipoxygenase and CL of the lecithin liposomes peroxidized with Fe2+ ions by 3 orders of magnitude. In the systems producing oxygen radicals (xanthine + xanthine oxidase and Fenton's reagent) EuT was ineffective. Luminol increased CL intensity up to 4 orders of magnitude in Fenton's reagent and by 2 orders of magnitude in xanthine oxidase reaction. The sensitization of CL in Fe2+-induced lipid peroxidation (LPO) of liposomes was by a factor 40, while in lipoxygenase reaction very low sensitization was observed. By means of cut-off light filter OS-12 (Soviet) having short wave-length transmittance limit at 560 nm it was possible to measure separately in the same sample the luminol-sensitized CL (maximal emission near 480 nm) and EuT-sensitized CL (maximum at 620 nm); these two CL components reflect, correspondingly, the production rate of oxygen- and lipid-free radicals. Mannitol, the OH radical scavenger, inhibited luminol-dependent component of CL in peroxidized liposomes and did not inhibited EuT sensitized CL in the same system. Apparently, hydroxyl radicals are produced in LPO reactions and responsible for the effect of CL sensitization by luminol, but are not involved in the chain LPO process.