EFFECTIVENESS OF PROTONS AND ARGON IONS IN INITIATING LIPID-PEROXIDATION IN LOW-DENSITY LIPOPROTEINS

In this study, human low-density lipoprotein (LDL) vesicles were irrad iated with 73 MeV protons (LET of 1 keV/mu m) and 11.4 MeV/nucleon arg on ions (LET of 1.52 MeV/mu m) and the effectiveness of charged partic les in initiating peroxidation of LDLs was investigated. The LDL suspe nsion (6 g/l) was exposed to protons and to argon ions in a dose range of 24 Gy to 2.4 kGy, Irradiations were carried out at the synchrocycl otron at the CPO and at the UNILAC of the GSI, After irradiation three chemical assays were used to study the progression of peroxidation of LDLs: the formation of conjugated dienes, the formation of thiobarbit uric acid-reactive substances (TBARS) and the increase in the relative electrophoretic mobility of the LDLs. The results were compared with those obtained after gamma irradiation. For protons the yields of the peroxidation products were 10 times lower than after gamma irradiation , However, for doses below 200 Gy, protons appeared to be more effecti ve than gamma rays in damaging the protein moiety, as deduced from the observed increase in the relative electrophoretic mobility of the LDL s, The irradiation with argon ions led to a negligible formation of pe roxidation products, but an increase in the relative electrophoretic m obility of the LDLs was observed, The results are indicative of a lowe r yield of lipid peroxidation after irradiation with high-LET particle s. In contrast, protons and argon ions appear to be more effective in inducing bulk protein and phospholipid damage than gamma rays. (C) 199 8 by Radiation Research Society.