title: Cadmium transport through type II alveolar cell monolayers: contribution of transcellular and paracellular pathways in the rat ATII and the human A549 cells.
abstract: Cadmium (CD) transport in alveolar type II (ATII) 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 (109)Cd 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 (v(i)) and equilibrium accumulation (A(max)) of (109)Cd 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 (109)Cd, with similar P(coeff) in both cell models, could not be exclusively related to cellular metal release. Results on 3H-mannitol permeability together with (109)Cd 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.
authors.affiliation: Département des Sciences Biologiques, Toxen, Université du Québec à Montréal, C.P. 8888, Succ. centre-ville, Montréal, Québec, Canada H3C 3P8. jumarie.catherine@uqam.ca
authors.forename: C
authors.initials: C
authors.lastname: Jumarie
mesh_terms: D000042:Absorption; D000818:Animals; D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism* / Q000633:toxicity; D002106:Cadmium Radioisotopes; D002460:Cell Line; D002463:Cell Membrane Permeability; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D008353:Mannitol / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D051381:Rats; D013997:Time Factors; D014316:Tritium
chemical_list: D002106:Cadmium Radioisotopes; D002104:Cadmium; D014316:Tritium; D008353:Mannitol