Mercury distribution in cortical areas and fiber systems of the neonatal and maternal adult cerebrum after exposure of pregnant squirrel monkeys to mercury vapor.

Pregnant squirrel monkeys were exposed 5 days/week to mercury vapor at a concentration of 0.5 mg Hg/m3 air for 7 hr/day, or at 1 mg Hg/m3 air for 4 or 7 hr/day. The calculated total mercury absorption ranged between 0.8 and 5.4 mg (range of daily absorption 0.04-0.07 mg). The mercury concentration in the cerebral occipital lobe of the offspring ranged between 0.20 and 0.70 microgram/g tissue, and in the mothers between 0.8 and 2.58 micrograms/g tissue. Mapping of the distribution of mercury in the neocortical layers of the maternal brains revealed that the pyramidal cells contained more visualized mercury than the other neurons. In addition, the mapping disclosed that the deeper the pyramidal cells were situated the more mercury they contained. In the offspring brains, no laminar distribution pattern was found. In the hippocampal formation, the pyramidal cells again contained more mercury than the other neurons. By contrast, the stratum granulosa of the dentate gyrus was always devoid of visualized mercury. The claustrum and the amygdaloid complex always contained mercury. In the fiber systems, the offspring brains contained more mercury than the adult brains. Mercury was found in both glial cells and neurons both in the cortical areas and in the fiber systems.