Fubini B, Mollo L, Giamello E
Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Università di Torino, Italy.
Free Radic Res. 1995 Dec;23(6):593-614. doi: 10.3109/10715769509065280.
The potential for free radical release has been measured by means of the spin trapping technique on three kinds of iron containing particulate: two asbestos fibers (chrysotile and crocidolite); an iron-exchanged zeolite and two iron oxides (magnetite and haematite). DMPO (5,5'-dimethyl-1-pirroline-N-oxide), used as spin trap in aqueous suspensions of the solids, reveals the presence of the hydroxyl and carboxylate radicals giving rise respectively to the two adducts [DMPO-OH] and [DMPO-CO2], each characterized by a well-defined EPR spectrum. Two target molecules have been considered: the formate ion to evidence potential for hydrogen abstraction in any biological compartment and hydrogen peroxide, always present in the phagosome during phagocytosis. The kinetics of decomposition of hydrogen peroxide has also been measured on all solids. Ferrozine and desferrioxamine, specific chelators of Fe(II) and Fe(III) respectively, have been used to remove selectively iron ions. Iron is implicated in free radical release but the amount of iron at the surface is unrelated to the amount of radicals formed. Only few surface ions in a particular redox and coordination state are active. Three different kinds of sites have been evidenced: one acting as H abstracter, the other as a heterogeneous catalyst for hydroxyl radical release, the third one related to catalysis of hydrogen peroxide disproportionation. In both mechanisms of free radical release, the Fe-exchanged zeolite mimics the behaviour of asbestos whereas the two oxides are mostly inert. Conversely magnetite turns out to be an excellent catalyst for hydrogen peroxide disproportionation while haematite is inactive also in this reaction. The results agree with the implication of a radicalic mechanism in the in vitro DNA damage and in the in vivo toxicity of asbestos.
两种石棉纤维（温石棉和青石棉）；一种铁交换沸石和两种铁氧化物（磁铁矿和赤铁矿）。在固体水悬浮液中用作自旋捕获剂的DMPO（5,5'-二甲基-1-吡咯啉-N-氧化物）揭示了羟基和羧酸盐自由基的存在，它们分别产生两种加合物[DMPO-OH]和[DMPO-CO2]，每种加合物都具有明确的电子顺磁共振光谱特征。考虑了两种靶分子：甲酸根离子以证明在任何生物区室中夺取氢的潜力，以及过氧化氢，在吞噬作用期间它总是存在于吞噬体中。还测定了所有固体上过氧化氢分解的动力学。分别用于选择性去除Fe(II)和Fe(III)的特异性螯合剂亚铁嗪和去铁胺已被使用。铁与自由基释放有关，但表面铁的量与形成的自由基量无关。只有处于特定氧化还原和配位状态的少数表面离子具有活性。已证明有三种不同类型的位点：一种作为氢夺取剂，另一种作为羟基自由基释放的非均相催化剂，第三种与过氧化氢歧化催化有关。在两种自由基释放机制中，铁交换沸石模仿石棉的行为，而两种氧化物大多是惰性的。相反，磁铁矿被证明是过氧化氢歧化的优良催化剂，而赤铁矿在该反应中也是无活性的。结果与自由基机制在体外DNA损伤和石棉体内毒性中的作用一致。
