Iron handling in the gut
journey of an iron ion
🏠 duodenum/jejunum
- most iron absorbed in duodenum and upper jejunum
total iron = 3-4g
| Location | Iron form | Transformation |
|---|---|---|
| The wild west brush border | Fe3+ | reduced to Fe2+ by ferric oxido-reductase OR ascorbate transported across membrane by DMT1 along with H+ |
| The wild west brush border | Complexed with haem | transported across membrane by DMT1 |
| Intracellular | Fe2+ | if complexed, liberated from haem by haem oxygenase Iron bound to apoferritin in cytoplasm |
| Its fate... | ferritin-bound Fe2+ | remains bound to ferritin intracellularly OR leaves via membrane transporter ferroportin |
🏠 iron is stored in liver, bone marrow or spleen
mobilisation when plasma iron ↓
- transported as transferrin
- binds to receptors in cell membrane of erythroblasts
- endocytosed → iron transported to mitochondria → haem synthesis
endocrine regulation: hepcidin
| Net effect: | inhibits iron uptake |
|---|---|
| Secreted from | Synthesised in liver |
| Stimulus | iron overload inflammation |
| Inhibition | hypoxia erythropoiesis (via erythroferrone)/EPO pregnancy |
| Acts on (action) | ↓ transcription of DMT1 gene degrades ferroportin |