Transport Kinetics of Iron Chelators and Their Chelates in Caco-2 Cells |
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Authors: | Xi-Ping Huang M Spino J J Thiessen |
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Institution: | (1) Leslie Dan Faculty of Pharmacy, University of Toronto, 19 Russell St., Toronto, Ontario, Canada, M5S 2S2;(2) ApoPharma, Toronto, Ontario, Canada |
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Abstract: | Purpose Caco-2 monolayers were used to contrast the bidirectional transport of iron chelators and their chelates and to estimate fundamental
kinetics associated with their intestinal absorption.
Methods Bidirectional transport was studied at 37°C and pH 7.4 using 500-μM concentrations. Monolayer integrity was tested via transepithelial
electrical resistance and sodium fluorescein permeability. Apical and basolateral analysis provided mass balance evidence.
Apparent permeability coefficient (Papp) served to rank and compare molecules and estimate in vivo bioavailability. Model-dependent rate constants defined cellular influx and efflux.
Results 1) Papp ranked in decreasing order for chelators from directional transport studies were CP363 > deferiprone> ICL670 > CP502 > deferoxamine
(DFO). 2) Fe(CP502)3, Fe(ICL670)2, and FeDFO were not measurable in receiving chambers, whereas Fe(deferiprone)3 and Fe(CP363)3 were detected in both directions. 3) CP363 was transported significantly faster from the basolateral to the apical direction
than the converse. 4) Mass balance of donor and receiver chambers gave approximately 100% recovery in all cases. 5) Kinetic
analysis supports the view that the Caco-2 chelator efflux constants are generally greater than their influx constants.
Conclusions Caco-2 cells are useful in screening iron chelators and chelates and estimating bioavailabilities. Structure and distribution
coefficients partially predict passive transport through Caco-2 monolayers. |
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Keywords: | Caco-2 cells iron chelate iron chelator iron overload |
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