METAL-INDUCED HYDROXYL RADICAL GENERATION BY CU-METALLOTHIONEINS FROMLEC RAT-LIVER()

Reactions of LEC (Long-Evans rats with a cinnamon-like coat color) rat liver Cu(I)-metallothioneins (MTs) with HgCl2 or K3Fe(CN)(6) were inv estigated by ESR spectroscopy and generation of hydroxyl radicals was demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), When Cu(I)-MTs were incubated with more than one equivalent m ole HgCl2 or K3Fe(CN)(6) to Cu+ bound to MTs, strong signals due to Cu 2+ appeared, ESR spectra, which were a combination of the DMPO-OH addu ct signal and a six-line signal, were observed in the reaction of Cu(I )-MTs with HgCl2, whereas no oxygen radical signal was seen with K3Fe( CN)(6). The DMPO-OH signal intensity was greater in the presence of SO D while the signal disappeared in the presence of catalase, The result s suggest that addition of HgCl2 causes the liberation of cuprous ions from MTs followed by a reaction with oxygen, leading to hydroxyl radi cal formation through a Fenton-type Haber-Weiss reaction. (C) 1997 Aca demic Press.