Regional distribution of lead in the brains of lead-intoxicated adult mice.

The susceptibility of adult neural tissues to the detrimental effects of Pb poisoning has prompted the present distributional analysis of lead in the brains of chronically lead-exposed mice. A high-resolution microPIXE method was developed for measuring Pb in whole-brain cryosections derived from chronically lead-exposed mice. Spatial resolutions as small as 20 micron were obtained. Details of the methodology are presented together with procedures for Pb standard preparation and control measures employed to reduce potential errors of Pb assay associated with taking brain sections with steel alloy knives. The unique advantages of making microPIXE Pb determinations in nonpreselected brain anatomic regions using freeze-dried semithick cryosections are reviewed. The study revealed that, in lead-intoxicated mice, there existed wide regional variation in Pb concentration in the ppm range, in 50 micron sagittal or coronal sections. Higher Pb levels were found in discrete brain regions of lead-treated adult mice than in matched control brains. Suggestions for further studies of Pb kinetics using microPIXE methods in adults and immature animals, including components of neural barrier tissues, are reviewed.