Author(s): Hu M, Borchardt RT
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Abstract The Caco-2 model system (Hidalgo et al., Gastroenterology, 96:736-749, 1989), which is a monolayer of polarized intestinal epithelial cells grown onto a porous polycarbonate membrane, was used to study the mechanism of transcellular transport of an antihypertensive agent, L-alpha-methyldopa (L-alpha-MD). The results showed that the transport of L-alpha-MD was pH, glucose, concentration, and temperature dependent, and it could be inhibited by metabolic inhibitors (e.g., 2,4-dinitrophenol) and by amino acids (e.g., L-phenylalanine) which have an affinity for the large neutral amino acid (LNAA) carrier. In addition, the apparent kinetic constants describing the transcellular transport of L-alpha-MD were altered depending on the time interval between feeding the cells and the transport experiments (postfeeding time, PFT). The apparent maximum carrier flux (Jmax) of L-alpha-MD was significantly increased (from 155 to 547 pmol/mg protein/min) when PFT was prolonged from 8.5 to 56 hr. These results indicated that the transcellular transport of L-alpha-MD through the polarized Caco-2 cell monolayer was carrier mediated via the LNAA carrier. The similarities in the characteristics of L-alpha-MD transport exhibited by the Caco-2 model system and other intestinal models in vitro further substantiate the usefulness of this cell culture model for studying the intestinal transport of nutrients and drugs.
This article was published in Pharm Res
and referenced in Journal of Bioequivalence & Bioavailability