Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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In the preceding work, the tissue distribution of multitracer was examined among 11 organs (brain, cardiac muscle, lung, liver, spleen, pancreas, kidney, bone, thighbone muscle, eyeballs and testes) in normal 6 weeks old mice, and evaluated in terms of gtissue uptake rateh in the organs (7). In figure 2, the brain uptake rates of Rb, Zn, Mn, Se, Sc, Co and Zr are shown at 6, 12, 24 and 48 h after i.p. injection. The values of Rb, Zn, Mn, Se and Sc were substantially larger than those of Co and Zr. The values of Co and Zr decreased with time. However, the values of Rb, Zn and Mn increased with time, that of Se reached a plateau at 3 h after injection. According to these strict comparison of these tracers in the brain, Mn, Zn, Se and Rb were found to remain for fairly long time in brain. It is thought that Mn, Zn and Se are essential and Rb is analogous to potassium.

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Fig. 3. Brain uptake rate of multitracer in C57BL/6N mice.

In the present work, the 3 tracers of Rb, Zn and Se are distributed fairly evenly in the all brain regions as shown in Fig.2. No significant difference of uptake rate is found among 4 different ages. On the other hand, the 3 tracers of Mn, Sc and Zr are not distributed uniformly,and highly concentrated in certain regions.
In hippocampus, the retention values of Sc, Mn and Zr are substantially increasing with aging. Especially in the aged mice, the Sc and Zr tracers are uptaken to 3-4 %dose/g and 0.1-0.2 %dose/g of regions, respectively, and the 2 tracers (Sc, Zr) are not significantly excreted and are remaining during long time in the brain.

The behaviors of Sc, Mn and Zr may be ascribed to the degenerative variation of the function of BBB due to aging. More detailed knowledge of the uptake behavior of essential Mn and non-essential Sc and Zr in brain regions is required for the involvement in their functions to maintain neuronal homeostasis such as neurotransmitter metabolism.

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