ENTRY OF LOW-DOSES OF MERCURY-VAPOR INTO THE NERVOUS-SYSTEM

Inorganic mercury remains within neurons indefinitely and has been imp licated in some human neurodegenerative diseases. We were interested i n finding the lowest dose of mercury vapor that resulted in mercury de position in neurons. Female BALB/c mice were exposed to 25 mu g mercur y/m(3) for 2-20 hr or 500 mu g mercury/m(3) for 5-240 min. To see if f emale mouse neurons were more susceptible to mercury vapor than male n eurons, male and female BALB/c mice were exposed to 50 mu g mercury/m( 3) for 4-24 hr. Mice were perfused with formalin 1-30 weeks after expo sure and paraffin sections of brain, spinal cord and kidney were stain ed for mercury with silver nitrate autometallography. On light microsc opy, spinal motor neurons contained mercury granules alter 12 hr expos ure to 25 mu g mercury/m(3) or alter 30 min exposure to 500 mu g mercu ry/m(3). Mercury remained in motor neurons 30 weeks alter exposure. In female mice, mercury was seen in motor neurons at hall the exposure t imes of male mice. In conclusion, low doses of mercury vapor, well wit hin WHO guidelines for sale human occupational exposure, enter and rem ain within motor neurons of mice. (C) 1998 Intox Press, Inc.