Effects of Reactive Oxygen Modulators on in vivo Demethylation of Methylmercury(PROCEEDINGS OF 24TH SYMPOSIUM ON TOXICOLOGY AND ENVIRONMENTAL HEALTH)

Abstract

To elucidate the involvement of reactive oxygen in in vivo demethylation of methylmercury(MeHg), the effects of paraquat (PQ) and other reactive oxygen modulators on inorganic-Hg (I-Hg) production in MeHg-administered rats were examined. Rats were intravenously (i.v.) injected with MeHgCl (2mg/kg). After MeHg administration, I-Hg levels time-dependently increased in the liver up to 9h, whereas the renal levels did not change during the first 3h, and then increased up to 24h in a time-dependent manner. PQ stimulated I-Hg production in the liver but not in the kidney, whereas it increased 2-thiobarbituric acid-reactive substance (TBA-RS) levels in both tissues. PQ-induced stimulation of I-Hg production was not further accelerated by an OH· enhancer, such as FeSO₄ or Fe(III)EDTA. Hepatic I-Hg production in MeHg-administered rats (without PQ) was suppressed by NaCN (a potent inhibitor of mitochondrial cytochorome oxidase) but not by desferal or Fe(III) EDTA (an OH· modulalator). These results suggest that hepatic mitochondria may play an important role in in vivo demethylation of MeHg, and that reactive oxygen species other than OH· may participate in it.