EFFECTS OF ADDITIONAL IRON-CHELATORS ON FE2-INITIATED LIPID-PEROXIDATION - EVIDENCE TO SUPPORT THE FE2+ FE3+ COMPLEX AS THE INITIATOR()

The addition of chelated Fe2+ ions in a liposomal system often results in a short lag period before peroxidation starts. The addition of a s econd chelator at the end of the lag period results in an inhibition o f the lipid peroxidation. The degree of inhibition depends ow the stab ility constants of the chelator in ligating Fe2+ and/or Fe3+. A more s triking inhibitory effect was observed for the chelators With higher s tability constant for either or both Fe2+- and Fe3+-complex, bat much less inhibition was found for those with lower stability constants for both complexes. Assuming that the ''initiator'' for iron-dependent li pid peroxidation is formed through the redox process of iron ion and f inally emerged at the end of the latent period, the inhibitory effect of the second chelator may be explained as the abstraction of either F e2+ or Fe3+ from the initiator by an additional free chelator, which r esults in the decomposition of the initiator. This study supports the hypothesis that a Fe2+... Fe3+ complex is responsible for iron-initiat ed lipid peroxidation.