Subcellular distribution of recently absorbed iron and of transferrin in the mouse duodenal mucosa.
A successful method for the analytical subcellular fractionation of mouse duodenal mucosa organelles was established. 59Fe(III)-nitrilotriacetate (pH 7.2) was injected into tied-off duodenal segments in vivo and, after 2-20 min, mucosal homogenates were subjected to subcellular fractionation. Radioactivity was recovered in the cytosolic fractions and in the gradient at a density of 1.18-1.20 g/ml. Enhanced iron absorption was achieved by placing the animals in a hypobaric chamber for 3 days. These animals had a higher proportion of particulate 59Fe compared to controls. Homogenisation in sucrose medium containing the selective plasma membrane perturbant digitonin shifted the particulate iron fraction to a higher density region of the gradient indicating a localisation of the iron binding site to the plasma membrane region of the mucosal cells. No significant radioactive iron was observed in the brush-border region of the gradient. Transferrin immunoreactivity was found only in the cytosolic region of the gradient and was not associated with any organelle.
Osterloh
K
K
Division of Clinical Cell Biology, MRC Clinical Research Centre, Harrow, Middlesex, U.K.
Snape
S
S
Simpson
R J
RJ
Grindley
H
H
Peters
T J
TJ
D000818:Animals; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004386:Duodenum / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D007501:Iron / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism*
D014168:Transferrin; D007501:Iron