Organic and inorganic mercury in neonatal rat brain after prenatal exposure to methylmercury and mercury vapor.
BACKGROUND
Many populations are exposed to multiple species of mercury (Hg), predominantly organic Hg as methylmercury (MeHg) from fish, and inorganic Hg as Hg vapor from dental amalgams. Most of our knowledge of the neurotoxicity of Hg is based on research devoted to studying only one form at a time, mostly MeHg.


OBJECTIVE
In this study we investigated the effects of prenatal exposure to MeHg and Hg vapor on Hg concentrations in the brain of neonatal rats.


METHODS
Female Long-Evans hooded rats were exposed to MeHg (0, 3, 6, or 9 ppm as drinking solution), Hg vapor (0, 300, or 1,000 microg/m3 for 2 hr/day), or the combination of both, from 30 days before breeding through gestational day 18. On postnatal day 4, whole brains were taken from one male and one female from each of four litters in each treatment group to assess organic and inorganic Hg in the brain by cold vapor atomic absorption spectrometry.


RESULTS
Statistical analysis using linear mixed effects models showed that MeHg dose was the primary determinant of both organic and inorganic brain Hg levels. For both outcomes, we also found significant interactions between MeHg and Hg vapor exposure. These interactions were driven by the fact that among animals not exposed to MeHg, animals exposed to Hg vapor had significantly greater organic and inorganic brain Hg levels than did unexposed animals.


CONCLUSIONS
This interaction, heretofore not reported, suggests that coexposure to MeHg and Hg vapor at levels relevant to human exposure might elevate neurotoxic risks.
Ishitobi
Hiromi
H
Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA.
Stern
Sander
S
Thurston
Sally W
SW
Zareba
Grazyna
G
Langdon
Margaret
M
Gelein
Robert
R
Weiss
Bernard
B
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D005260:Female; D008628:Mercury / Q000009:adverse effects / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000009:adverse effects / Q000378:metabolism*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans
D008767:Methylmercury Compounds; D008628:Mercury