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The ontogeny of intestinal iron absorption in the guinea pig

Chowrimootoo, George Francis Emmanuel; (1994) The ontogeny of intestinal iron absorption in the guinea pig. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

omeostasis of body iron content is regulated by intestinal iron absorption. In neonatal animals however, absorption of iron is enhanced despite having substantial iron stores. In order to examine the cellular basis for this effect, intestinal iron absorption has been compared in adult and neonatal guinea pigs using a variety of techniques. Iron measurement has shown the neonates are not iron deficient compared to the adult. Studies carried out in vivo using radiolabelled iron confirmed previous studies that the rate of duodenal iron transfer in the adult was an order of magnitude greater than that of the terminal 20 cm of ileum. In the neonate however, the rate of transfer was similar in both duodenum and ileum. Transition to the adult duodenal/ileal ratio occurs after the first 16 days of postnatal life. This localisation change may be relevant to the enhanced iron absorption in neonatal mammals. Several approaches, including autoradiography of everted duodenal and ileal segments and uptake of iron by duodenal and ileal brush border membrane vesicles, confirmed that the regulatory site for iron absorption is not at the brush border membrane. Chromatographic and immunoprecipitation studies of enterocyte cytosolic iron binding proteins showed that in the adult 30-40% of newly absorbed iron was associated with ferritin. Some was associated with a protein of low molecular weight of about 10-12 kD. In contrast, in newborn animals and those up to 21 days old, 80[percent] of newly absorbed radioactive iron was found to be associated with this low molecular weight protein. These results were confirmed by parallel immunoblotting studies which showed the levels of ferritin to be low in newborn but increased with age. Similarly the levels of the low molecular weight protein was shown to be high at birth and decrease during development. Studies of transferrin receptor number using isolated duodenal and ileal enterocytes indicated that changes in transferrin binding was not responsible for the developmental changes in intestinal iron absorption. The results presented in this thesis throw further light on the mechanisms regulating intestinal iron absorption during development. It is concluded that neither brush border membrane transport nor events involving transferrin binding to enterocytes account for the enhanced iron absorption in the neonate. Changes in iron absorption during development may be explained by segmental or enterocyte maturation differences, intracellular events involving iron binding proteins or differences in iron handling by the basolateral membrane.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The ontogeny of intestinal iron absorption in the guinea pig
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10105986
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