Inhaled iron, unlike manganese, is not transported to the rat brain via the olfactory pathway.
Iron and manganese share structural, biochemical, and physiological similarities. The objective of this study was to determine whether iron, like manganese, is transported to the rat brain via the olfactory tract following inhalation exposure. Eight-week-old male CD rats were exposed to approximately 0.31 mg Fe per m(3) (mass median aerodynamic diameter = 2.99 microm; geometric standard deviation = 1.15) via inhalation for a target duration of 90 min. Following exposure, rats were euthanized immediately (0) or at 1, 2, 4, 8, or 21 days postexposure. In addition to nasal and regional brain tissues, blood, and viscera were also collected. 59Fe concentrations were determined by gamma spectrometry. Further, heads were collected and frozen, and autoradiograms were prepared to visualize the location of 59Fe from the nose to the brain. Finally, olfactory mucosa samples collected at 0, 2, 4, and 21 days postexposure were further analyzed using high-performance liquid chromatography (HPLC) plus gamma spectroscopy to determine the association between 59Fe and transferrin. Data obtained from gamma spectrometry revealed that most of the iron remained in the nasal regions of the olfactory system and that less than 4% of iron deposited on the olfactory mucosa was observed in the olfactory bulb. Autoradiograms confirmed the data obtained from gamma spectrometry. 59Fe activity was absent in the olfactory regions of the brain even 4 days postexposure. Further, HPLC-gamma spectroscopy analyses indicated that 59Fe in the olfactory mucosa was coeluted with transferrin. Hence iron, unlike manganese, is not readily transported to the brain via the olfactory tract.
Rao
Deepa B
DB
CIIT Centers for Health Research, Research Triangle Park, NC 27709-2137, USA. drao@ciit.org
Wong
Brian A
BA
McManus
Brian E
BE
McElveen
Anna M
AM
James
Andrew R
AR
Dorman
David C
DC
D000280:Administration, Inhalation; D000818:Animals; D001345:Autoradiography; D001692:Biological Transport; D001921:Brain / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism; D007501:Iron / Q000097:blood / Q000493:pharmacokinetics* / Q000633:toxicity; D007504:Iron Radioisotopes / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000493:pharmacokinetics; D009830:Olfactory Bulb / Q000378:metabolism; D009831:Olfactory Mucosa / Q000378:metabolism; D009833:Olfactory Pathways / Q000378:metabolism*; D011897:Random Allocation; D051381:Rats; D013051:Spectrometry, Gamma; D014168:Transferrin / Q000378:metabolism
D007504:Iron Radioisotopes; D014168:Transferrin; D008345:Manganese; D007501:Iron