Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1564, Issue 2, Pages 487-499Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S0005-2736(02)00499-6
Keywords
cadmium; metal transport; epithelium permeability; paracellular barrier; type II cell; A549 cell
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Cadmium (Cd) transport in alveolar type II (ATTII) cells has been studied using two in vitro models widely used to investigate lung function: primary cultures of rat ATII cells and the human cell line A549. Nonlinear regression analyses of the uptake time-course of Cd-109 revealed: a zero-time accumulation, a fast process of accumulation which proceeds within minutes, and a much slower process which takes hours. This three-step mechanism was characterized by different parameter values under dishes-or filter-growth conditions. A higher initial uptake rate (vi) and equilibrium accumulation (A(max)) of Cd-109 were found in the rat ATII cells; these differences were not related to a higher level of adsorption onto the external surface of the cell membrane. Specific transport systems of similar capacity but different affinity (threefold higher in rat cells) were characterized. A significant transepithelial transport of Cd-109, with similar P-coeff in both cell models, could not be exclusively related to cellular metal release. Results on H-3-mannitol permeability together with 109Cd efflux data strongly suggest a greater contribution of the paracellular pathways in Cd transport through A549 cell monolayers. These differences in transport properties between the two lung cell models may modify the dose-response curve for Cd toxicity. (C) 2002 Elsevier Science B.V. All rights reserved.
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