Does selenium deficiency unmask mercury toxicity in motor neurons?
OBJECTIVE
Inorganic mercury enters in particular motor neurons and has been implicated in motor neuron diseases. One way that cells protect themselves from mercury toxicity is via selenium, so we sought to determine whether the motor neurons of mice on a low selenium diet would be more susceptible to mercury toxicity.


METHODS
Recently weaned mouse pups were placed on diets containing either low, normal or high levels of selenium. Twenty days later, half were exposed to mercury vapor. Ninety days after exposure, their spinal motor neurons and phrenic motor axons were examined histologically. Mercury in the spinal cord was sought using autometallography.


RESULTS
Neither low nor high selenium diets combined with mercury vapor had any clinical effect on the mice. Mercury was seen within the spinal motor neurons of all exposed mice. Spinal motor neurons and phrenic motor axons however appeared normal in morphology and size across the groups.


CONCLUSIONS
Diets low or high in selenium did not damage motor neurons with or without mercury. This suggests that changes in the selenium environment are unlikely to precipitate mercury toxicity in motor neurons.
Pamphlett
Roger
R
Department of Pathology D06, The University of Sydney, Sydney, New South Wales 2006, Australia. rogerp@med.usyd.edu.au
Eide
Rune
R
Danscher
Gorm
G
D000818:Animals; D000831:Animals, Newborn; D018753:Diet, Protein-Restricted / Q000379:methods; D005260:Female; D008297:Male; D008628:Mercury / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D009046:Motor Neurons / Q000187:drug effects* / Q000473:pathology; D010791:Phrenic Nerve / Q000187:drug effects / Q000473:pathology; D011247:Pregnancy; D012643:Selenium / Q000172:deficiency*; D013116:Spinal Cord / Q000166:cytology*
D008628:Mercury; D012643:Selenium