Nickel permeation pathways in the small intestine and the olfactory systemTallkvist, Jonas
For most people the body burden of nickel results primarily from ingestion ofthe metal in food and drinking water. In addition, inhaled air constitutes an important route of occupational nickel exposure.
The present studies have aimed at characterizing the intestinal nickel absorption, and at determining whether nickel is taken up from the olfactory mucosa into the brain via the olfactory neurons and the mechanisms forsuch a potential uptake.
Studies with perfused rat intestinal segmentsshowed that nickel absorption is higher in the jejunum than in the ileum. Several observations indicated that the nickel is absorbed actively through the jejunal epithelium. Studies with perfused intestinal segments of irondeficientrats indicated that nickel, at least partly, shares the transport mechanism for iron. In these perfusions the nickel concentration in the absorbates even exceeded the nickel concentration in the perfusates.
Oral auminisuauon resulted m nrgner mcKei levels in several tissues of iron-deficient rats as compared to controls. These data support the assumption that nickel is taken up from the intestines by the iron transport mechanism. Studies in which rats were given nickel intraperitoneally indicate that the iron-status also affects the uptake of nickel from the blood into the tissues.
Studies on the transport of nickel across Caco-2 cells showed a passage of the metal over the epithelium in both directions. The results indicated that die transport occurred actively, with no paracellular passage in intact monolayers, and that also in the Caco-2 cells the nickel may participate in an absorptive process for iron.
Intranasal instillation of nickel in rats resulted in an uptake of the metal in the olfactory epithelium and a migration along primary olfactory axons to the glomeruli ofthe olfactory bulbs, and further to the rostral parts ofthe cerebral hemispheres.
Studies in pikes, in which nickel was applied in the olfactory chambers, showed that the metal was transported by slow axonal transport in the primary olfactory neurons. Cell fractionations and gel filtrations of the olfactory tissues of pikes and rats showed that nickel was bound both to particulate and cytosolic cellular constituents.
Keywordsnickel; mechanisms; intestinal absorption; in vitro perfusion; Caco-2 cell culture; iron-status; olfactory system; slow axonal transport; brain; rat; pike
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
1997, number: 26
Publisher: Swedish University of Agricultural Sciences
UKÄ Subject classification
Pharmacology and Toxicology
URI (permanent link to this page)