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Abstract

Cell culture models for gastrointestinal transport and metabolism are important mechanistic tools. Our studies of Caco-2 monolayers demonstrate heterogeneity in transport characteristics depending on passage number and origin of the cells. In accordance with data obtained in animals and humans, TRH shows a carrier-mediated, saturable transport component, which operates parallel to a passive pathway in Caco-2 cells at passage number 89-99. At low TRH concentrations (< 3 mM) active transport becomes prominent, as demonstrated by the temperature dependence of TRH transport and inhibition experiments. The Michaelis-Menten parameters of the active, saturable transport component are: Km = 1.59 mM and Vmax = 1.84 microM/min. The pH optimum was determined to be at pH 6.0. On the other hand an exclusively paracellular passive route was found with Caco-2 cells at passage number 30-34. These results are also in agreement with observations made by others in cell culture experiments. The aspect of rigorously characterizing the specific Caco-2 clone under investigation is emphasized, especially when active transport mechanisms are suspected.

Transepithelial Transport of PAMAM Dendrimers across Isolated Rat Jejunal Mucosae in Ussing Chambers

“…In comparison to in vivo models, Caco-2 cell monolayers lack mucus layers, extracellular matrix proteins, supportive mixed cell populations, basement membranes, and metabolic protein expression. Indeed, Caco-2 cell cultures can give a wide range of transport data based on differences between source, , selection pressure, passage number, and tissue culture conditions. − Caco-2 cells have been noted for their increased sensitivity to penetration enhancers, excessively high resistant tight junctions and increased indications of cytotoxicity upon exposure to enhancers compared to native isolated rat and pig intestinal tissue. , Thus, to account for such deficiencies in Caco-2 cells, we evaluated the mechanism of dendrimer permeability and toxicity in an isolated rat jejunal model in Ussing chambers.…”

HT29-MTX/Caco-2 Cocultures as an in Vitro Model for the Intestinal Epithelium: In Vitro–in Vivo Correlation with Permeability Data from Rats and Humans

“…The Caco-2 cell line, a well-differentiated human intestinal cell line, has been investigated as a potential in vitro model for oral drug absorption and metabolism studies. 2,4,[7][8][9][10] When Caco-2 cells are grown on microporous membranes, they form a confluent monolayer with several properties characteristic of differentiated enterocytes in the small intestine. 11,12 The monolayers are morphologically polar and develop brush borders at their apical surface.…”