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

Abstract

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)

Mercury Accumulation in Harbour Seals from the Northeastern Pacific Ocean: The Role of Transplacental Transfer, Lactation, Age and Location

“…The increase observed here between mid and late gestation is consistent with studies showing an increased THg transfer from the mother to the fetus associated with increased blood flow at the end of the gestation period in rats, hamsters, and guinea pigs (Inouye and Kajiwara 1988;Nordenhall et al 1995;Yoshida et al 2002). Habran et al (2013) also concluded that Hg was transferred to grey seal (Halichoerus grypus) pups during gestation by analyzing Hg levels in the lanugo.…”

Mercury and lead during breast-feeding

“…Experiments show that Hg acquisition in early life is more quantitatively significant during the prenatal period than during breast-feeding (Mansour et al 1973;Nordenhall et al 1995;Vimy et al 1997;Sakamoto et al 2002). Nordenhall et al (1995) reported that when hamsters were injected with labelled Hg, 11 % of the dose appearing in the litter was transferred via the placenta while only 1•7 % was transferred via milk. Similar effects were observed in rats fed 5 parts per million MMeHg during gestation and lactation.…”

Neurobehavioural and molecular changes induced by methylmercury exposure during development

“…Dietary MeHg is nearly completely absorbed in the gastrointestinal tract (Clarkson, 1972). In addition to having a more sensitive nervous system infants are also believed to have lower excretion capacity for MeHg (Nordenhäll et al, 1998), further increasing their vulnerability to this substance. MeHg crosses the placenta, with higher levels in fetal cord blood compared to maternal blood (Vahter et al, 2000).…”