Microtranslocation of trace element in the olfactory bulb of mice after intranasal instillation of fine oxide particle by synchrotron radiation X-ray fluorescence

The contents and micro distribution of iron and other trace elements in the olfactory bulb after intranasal instillation were measured by synchrotron radiation X-ray fluorescence analysis (SRXRF). The mice were intranasally instilled of fine iron oxide particles (60-200 nm) at a dose of 40 mg/kg body weight. Two weeks later, the content of iron in the olfactory bulb increased 20% compared with the control. The elevated iron was predominately concerned in the olfactory nerve (ON), granular layer (Gl) and anterior olfactory nucleus, external part (AOE), which indicated that fine iron oxide was transported to Gl via primary olfactory nerve and further translocated in AOE via secondary olfactory nerve. Moreover, in the experiment group, the levels of Ca increased 12% and Zn decreased 17%. Similarly to Fe, the higher Ca concentration was dominantly accumulated in the ON and Gl layers as well. Although the average Cu content in the control and experimental group was similar, the distribution of Cu was obviously changed due to the exposure of fine Fe₂O₃ particles. In the control, Cu was primarily concerned in anterior olfactory nucleus, lateral part (AOL), AOE, accessory olfactory bulb (AOB) and granule cell layer of the accessory olfactory bulb (GrA), while the Cu content in the experimental group was significantly higher in the ON, Gl and EP1 layers. In conclusion, the changes of Fe, Ca, Zn, Cu levels must be, to some extent, correlate with the oxidative stress and neurodegenerative diseases.