Cobalt(II) and nickel(II) ions as promoters of free radicals in vivo: detected directly using electron spin resonance spectrometry in circulating blood in rats.

We employed an electron spin resonance (ESR)2 spectrometer and used a direct detection technique for determining free radicals in circulating blood in rats. We found that the simultaneous intravenous injection of CoCl2 (10-500 mM) and ascorbic acid (100 mM) led to the formation of ascorbic acid free radicals. The potential of the Co(II) salt for producing ascorbic acid radicals was found to be dose-dependent, and was 10-fold stronger than that of a Fe(III) salt. Low height signals of the ascorbic acid radical were also observed during the simultaneous injection of NiCl2 (500 mM) and ascorbic acid (100 mM). This study clearly demonstrated that the metal ions of iron family are promoters of free radicals in vivo. These results also provide evidence to support the speculation based predominantly on in vitro experiments, that the mechanism responsible for the toxicity produced by excessive intake of transitional metal ions may involve the formation of free radicals.