Heme Iron Uptake by Caco-2 Cells is a Saturable,Temperature Sensitive and Modulated by Extracellular pH and Potassium |
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Authors: | Miguel Arredondo Janneke Kloosterman Sergio Núñez Fabián Segovia Valeria Candia Sebastián Flores Solange Le Blanc Manuel Olivares Fernando Pizarro |
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Institution: | (1) Laboratorio de Micronutrientes, INTA, Universidad de Chile, Casilla 138-11, Santiago, Chile;(2) Section of Human Nutrition and Epidemiology, Wageningen University, Wageningen, The Netherlands |
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Abstract: | It is known that heme iron and inorganic iron are absorbed differently. Heme iron is found in the diet mainly in the form
of hemoglobin and myoglobin. The mechanism of iron absorption remains uncertain. This study focused on the heme iron uptake
by Caco-2 cells from a hemoglobin digest and its response to different iron concentrations. We studied the intracellular Fe
concentration and the effect of time, K+ depletion, and cytosol acidification on apical uptake and transepithelial transport in cells incubated with different heme
Fe concentrations. Cells incubated with hemoglobin-digest showed a lower intracellular Fe concentration than cells grown with
inorganic Fe. However, uptake and transepithelial transport of Fe was higher in cells incubated with heme Fe. Heme Fe uptake
had a low V
max and K
m as compared to inorganic Fe uptake and did not compete with non-heme Fe uptake. Heme Fe uptake was inhibited in cells exposed
to K+ depletion or cytosol acidification. Heme oxygenase 1 expression increased and DMT1 expression decreased with higher heme
Fe concentrations in the media. The uptake of heme iron is a saturable and temperature-dependent process and, therefore, could
occur through a mechanism involving both a receptor and the endocytic pathway. |
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Keywords: | Heme Fe absorption Bioavailability Uptake Transport Caco-2 cells |
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