Are Developmental Changes in Methylmercury Metabolism and Excretion Mediated by the Intestinal Microflora?

Rowland, Ian; Robinson, R. D.; Doherty, Richard A.; Landry, Timothy D.

doi:10.1007/978-1-4615-9346-1_32

Cited by 21 publications

(12 citation statements)

References 22 publications

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“…Rowland and his colleagues (23) have reported that microflora in the suckling animal lacked the capacity to demethylate methylmercury, as indicated in figure 12. Two types of studies were carried out.…”

Section: Metabolism Of Metals In Reproduction and Developmentmentioning

confidence: 99%

Reproductive and developmental toxicity of metals.

Clarkson¹,

Nordberg²,

Sager³

1985

Scand J Work Environ Health

134

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Section: Metabolism Of Metals In Reproduction and Developmentmentioning

confidence: 99%

Reproductive and developmental toxicity of metals.

Clarkson¹,

Nordberg²,

Sager³

1985

Scand J Work Environ Health

134

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“…In contrast, most of the inorganic Hg, which is not easily absorbed in the intestines, is eliminated with the faeces (WHO 1990). Before weaning, rats (Thomas et al 1982(Thomas et al & 1988, mice (Doherty 1977;Rowland et al 1983;Shi et al 1990) and monkeys (Lok 1983) excrete MeHg at a low rate. The site and mechanism of demethylation is not fully understood.…”

mentioning

confidence: 99%

“…Thus, the demethylation of MeHg to inorganic Hg is a critical step in the process of elimination. The increase in the excretion rate at the time of weaning may be due to: 1) changes in intestinal microflora (Rowland et al 1983), 2) increased glutathione excretion leading to increased biliary excretion of both MeHg and Hg (Ballatori & Clarkson 1985), and 3) decreased intestinal absorption of inorganic Hg (Kostial et al 1983). Probably, the liver is the main site of demethylation, but some MeHg may be demethylated by the microflora in the intestines, as shown in rats (Rowland et al 1980).…”

mentioning

confidence: 99%

Transplacental and Lactational Exposure to Mercury in Hamster Pups after Maternal Administration of Methyl Mercury in Late Gestation

Nordenhäll

Dock

Vahter

1995

Pharmacology & Toxicology

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Pregnant Syrian golden hamsters were given a single oral dose of 203Hg-labelled methyl mercury (MeHg), 1.6 mumol/kg body weight, on day 12 of gestation. The uptake, retention and tissue distribution of 203Hg in the dams and pups was studied by gamma-counting during the following three weeks. The average transplacental transfer of 203Hg was 1.1% of the administered dose per pup, corresponding to 11% of the administered dose to a whole litter. This was considerably more than in our previous studies when the dams were treated on gestational day 2 (1.3%) or 9 (4.6%). The amount of 203Hg transferred to each pup in utero was independent of the litter size. The average additional transfer of 203Hg to a litter via milk was 1.7% of the administered dose. In the pups, the content of 203Hg in the liver and brain decreased, while the content in the kidneys and pelt increased during the second and third week. The highest amount of 203Hg was generally found in the pelt, which indicated that unweaned hamster pups primarily excrete MeHg by binding to hair. The chemical form of mercury in the liver and kidneys of the pups was determined by ion-exchange separation of inorganic Hg and MeHg followed by gamma-counting. The amount of inorganic Hg in the liver of the pups remained constant throughout the experiment, while it increased in the kidneys after one week due to the demethylation of MeHg. The inorganic Hg in the liver of newborn pups was probably due to maternal demethylation of MeHg and transplacental transfer of inorganic Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Composition of the microbiota in different developmental stages was shown to influence the MMHg demethylation capacity [79]. Fecal suspensions from suckled infants demethylated MMHg much slower than those from older children, and feces from children aged 10 months on a milk diet also showed a lower rate of demethylation than those from children of similar age consuming solid diets.…”

Section: Intestinal Methylation and Demethylation Of Hgmentioning

confidence: 99%

Biotransformation of metal(loid)s by intestinal microorganisms

Diaz-Bone

Wiele

2010

Pure and Applied Chemistry

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Many metals and metalloids undergo complex biotransformation processes by micro organisms in the environment, namely, Ge, As, Se, Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po. Though the human intestine harbors a highly diverse and metabolically active microbial community, the knowledge on metal(loid) biotransformation by gut microbiota is limited. Microbial metal(loid) metabolism in the gut is highly relevant when assessing health risks from oral exposure, as both the bioavailability and the toxicity of the ingested compound can be modulated. This review gathers and compares a broad selection of scientific studies on the intestinal biotransformation of metal(loid)s.It can be inferred that metal(loid) biotransformation by intestinal microbiota is a common process, resulting in both beneficial and adverse toxicological effects. Whereas for Hg the intestinal demethylation of methylmercury results in enhanced elimination, highly bioavailable and toxic arsenic and Bi species are formed by intestinal microorganisms. In either case, we conclude that the gut microbial potency should be considered to be taken up in toxicokinetic studies and models for assessing the health risks of oral metal(loid) exposure. This will allow the relevance of intestinal metal(loid) biotransformation to be assessed for human health risks.

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Are Developmental Changes in Methylmercury Metabolism and Excretion Mediated by the Intestinal Microflora?

Cited by 21 publications

References 22 publications

Reproductive and developmental toxicity of metals.

Reproductive and developmental toxicity of metals.

Transplacental and Lactational Exposure to Mercury in Hamster Pups after Maternal Administration of Methyl Mercury in Late Gestation

Biotransformation of metal(loid)s by intestinal microorganisms

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