Figure 3

Ferritin iron is taken up and transported by duodenal epithelium. (A) Wild type mice were fed equal counts of ⁵⁹FeCl₃ mixed with unlabeled N2a cells (lanes 1 and 3) or ⁵⁹Fe-labeled N2a cells (lanes 2 and 4) and chased for 4 hours. Homogenates of duodenum (lanes 1 and 2) or methanol precipitated protein from duodenum samples (lanes 3 and 4) were fractionated on a native gel and subjected to autoradiography (lanes 1-4). Lysates from ⁵⁹Fe-labeled N2a cells were fractionated in parallel (lane 5). Significantly more ⁵⁹Fe-ferritin is detected in mice fed with ⁵⁹FeCl₃ relative to ⁵⁹Fe-N2a homogenates (lanes 1 and 3 vs. 2 and 4). The ⁵⁹Fe-ferritin signal is from duodenal ferritin, not N2a ferritin (compare lanes 1-4 with lane 5). ⁵⁹Fe-labeled transferrin (Tf) is also detected in the N2a sample (lane 5) [22, 23](B) Quantification of ⁵⁹Fe incorporated by brain, liver and spleen of these mice shows relatively less uptake by mice fed with ⁵⁹Fe-labeled N2a homogenates relative to ⁵⁹FeCl₃. The data are representative of 3 independent experiments.