Regional distribution of metallothionein, zinc, and copper in the brain ofdifferent strains of rats

The regional brain distribution of metallothionein (MT), zinc, and copper i n the brain was determined in nine anatomical regions (olfactory bulb, cort ex, corpus striatum, hippocampus, thalamus plus hypothalamus, pens plus med ulla oblongata, cerebellum, midbrain, and white matter) and was compared be tween two different strains of rat (Sprague-Dawley [SD] and Lewis). No sign ificant difference was observed in the whole-brain MT level between the two strains (17.8 +/- 3.4 mu g/g in SD rats and 20.3 +/- 2.3 mu g/g in Lewis r ats). In SD rats, however, MT was more highly expressed in the white matter than in the other regions studied. In contrast, MT concentration was highe st in the cortex and lowest in the olfactory bulb in Lewis rats. The MT lev els in the cortex, corpus striatum, hippocampus, and thalamus plus hypothal amus were significantly lower in SD rats than in Lewis rats. In both strain s, the olfactory bulb contained markedly higher levels of both zinc and cop per than the other regions (27.9 +/- 6.8 mu g/g zinc in SD rats and 27.6 +/ - 6.9 mu g/g zinc in Lewis rats, and 5.2 +/- 1.5 mu g/g copper in SD rats a nd 11.1 +/- 4.8 mu g/g copper in Lewis rats). The next high-est zinc levels were seen in the hippocampus, whereas the next highest copper levels were in the corpus striatum in both SD and Lewis rats. The high levels of zinc a nd copper in the olfactory bulb were not accompanied by concomitant high MT concentrations. These results indicate that the strain of rat as well as t he anatomical brain region should be taken into account in MT and metal dis tribution studies. However, the highest concentrations of zinc and copper i n olfactory bulb were common to both SD and Lewis rats. The discrepancy bet ween MT and the metal levels in olfactory bulb suggests a role for other pr oteins in addition to MT in the homeostatic control of zinc and copper.