title: Identification and distribution of mercury species in rat tissues following administration of thimerosal or methylmercury.
abstract: Methylmercury (Met-Hg) is one the most toxic forms of Hg, with a considerable range of harmful effects on humans. Sodium ethyl mercury thiosalicylate, thimerosal (TM) is an ethylmercury (Et-Hg)-containing preservative that has been used in manufacturing vaccines in many countries. Whereas the behavior of Met-Hg in humans is relatively well known, that of ethylmercury (Et-Hg) is poorly understood. The present study describes the distribution of mercury as (-methyl, -ethyl and inorganic mercury) in rat tissues (brain, heart, kidney and liver) and blood following administration of TM or Met-Hg. Animals received one dose/day of Met-Hg or TM by gavage (0.5 mg Hg/kg). Blood samples were collected after 6, 12, 24, 48, 96 and 120 h of exposure. After 5 days, the animals were killed, and their tissues were collected. Total blood mercury (THg) levels were determined by ICP-MS, and methylmercury (Met-Hg), ethylmercury (Et-Hg) and inorganic mercury (Ino-Hg) levels were determined by speciation analysis with LC-ICP-MS. Mercury remains longer in the blood of rats treated with Met-Hg compared to that of TM-exposed rats. Moreover, after 48 h of the TM treatment, most of the Hg found in blood was inorganic. Of the total mercury found in the brain after TM exposure, 63% was in the form of Ino-Hg, with 13.5% as Et-Hg and 23.7% as Met-Hg. In general, mercury in tissues and blood following TM treatment was predominantly found as Ino-Hg, but a considerable amount of Et-Hg was also found in the liver and brain. Taken together, our data demonstrated that the toxicokinetics of TM is completely different from that of Met-Hg. Thus, Met-Hg is not an appropriate reference for assessing the risk from exposure to TM-derived Hg. It also adds new data for further studies in the evaluation of TM toxicity.
authors.affiliation: Faculdade de Ciências Farmacêuticas de Ribeirão Preto--FCFRP, Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, USP, Avenida do Café, s/n, Monte Alegre, Ribeirão Preto, SP 14040-903, Brazil.
authors.forename: Jairo L
authors.initials: JL
authors.lastname: Rodrigues
authors.forename: Juliana M
authors.initials: JM
authors.lastname: Serpeloni
authors.forename: Bruno L
authors.initials: BL
authors.lastname: Batista
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Souza
authors.forename: Fernando
authors.initials: F
authors.lastname: Barbosa
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002853:Chromatography, Liquid; D007668:Kidney / Q000378:metabolism; D008099:Liver; D008297:Male; D013058:Mass Spectrometry; D008628:Mercury / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000493:pharmacokinetics*; D009206:Myocardium / Q000378:metabolism; D011310:Preservatives, Pharmaceutical / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D013849:Thimerosal / Q000493:pharmacokinetics*
chemical_list: D008767:Methylmercury Compounds; D011310:Preservatives, Pharmaceutical; D013849:Thimerosal; D008628:Mercury