FORMATION OF FREE-RADICALS IN OXIDATION OF HUMAN LOW-DENSITY-LIPOPROTEIN - AN EPR SPIN-TRAPPING STUDY

The EPR spin trapping method with PBN as a spin trap was used to study the formation of free radicals in human low-density lipoprotein (LDL) upon ageing at 37 degrees C. The PEN associated radicals could be obs erved after 10 - 20 hours of incubation, depending on the pretreatment of LDL and the individual donor. The radicals observed in the first p eriod of time (until about 20 - 25 hours of incubation) are related to the degradation products of PBN. After that, additional radicals asso ciated with lipids are observed. The presence of EDTA does not prevent the process. The present experiments prove that some relatively fast oxidation process takes place in LDL incubated at physiological temper ature. The process is mild, as judged from the essentially unchanged c oncentration of thiobarbituric acid-reactive substances (TBARS). An ac tive role of the spin trap is not excluded.