Proline uptake by monolayers of human intestinal absorptive (Caco-2) cells in vitro

Nicklin, Paul; Irwin, W. J.; Hassan, Ian F.; Mackay, Martin

doi:10.1016/0005-2736(92)90042-k

Cited by 47 publications

(15 citation statements)

References 35 publications

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“…Conflicting results reported in the literature concern the driving force (Na ϩ or H ϩ gradients), the localization of the transporters and the contribution of diverse amino acid transporters such as systems A, B, IMINO, and others to the overall proline uptake (for review and discussion, see Chen et al, 2003). Even among studies using one particular model, the Caco-2 cell, the results are on first sight incompatible (Nicklin et al, 1992;Thwaites et al, 1993b;Berger et al, 2000;Chen et al, 2003). Now that PAT1 has been cloned and studied functionally, the remaining problems will soon be resolved.…”

Section: Discussionmentioning

confidence: 99%

Transport of Pharmacologically Active Proline Derivatives by the Human Proton-Coupled Amino Acid Transporter hPAT1

Metzner

Kalbitz²,

Brandsch³

2004

J Pharmacol Exp Ther

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Several proline derivatives such as L-azetidine-2-carboxylic acid, cis-4-hydroxy-L-proline, and 3,4-dehydro-DL-proline prevent procollagen from folding into a stable triple-helical conformation, thereby reducing excessive deposition of collagen in fibrotic processes and the growth of tumors. This study was performed to investigate whether the recently discovered human proton-coupled amino acid transporter 1 (hPAT1) is capable of transporting such pharmacologically relevant proline derivatives and also GABA analogs. Uptake of L- 3 H]proline uptake and flux inhibition. We conclude that 1) the substrate specificity of hPAT1 is very much broader than so far reported and 2) the system accepts therapeutically relevant proline and GABA derivatives. hPAT1 is a promising candidate for new ways of oral drug delivery.

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Section: Discussionmentioning

confidence: 99%

Transport of Pharmacologically Active Proline Derivatives by the Human Proton-Coupled Amino Acid Transporter hPAT1

Metzner

Kalbitz²,

Brandsch³

2004

J Pharmacol Exp Ther

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“…Previous studies on Caco-2 cells done with a variety of soluble molecules have shown that transport occurs only after cell polarization (13). Caco-2 cells have been shown to express the transport systems of nutrients, such as carbohydrates (1,24), amino acids (11,31), dipeptides (45), and bile acids (12), only when they acquire other properties of differentiated enterocytes. In our studies (Fig.…”

Section: Discussionmentioning

confidence: 99%

Expression and localization of organic cation/carnitine transporter OCTN2 in Caco-2 cells

Elimrani

Lahjouji

Seidman

et al. 2003

American Journal of Physiology-Gastrointestinal and Liver Physi

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Carnitine is derived both from dietary sources and biosynthesis. Dietary carnitine is absorbed in the small intestine and then distributed to other organs. Previous studies using Caco-2 cells demonstrated that the transport of L-carnitine in the intestine involves a carrier-mediated system. The purpose of this study was to determine whether the uptake of L-carnitine in Caco-2 cells is mediated by the recently identified organic cation/carnitine transporter (OCTN2). Kinetics of L-[ 3 H]carnitine uptake were investigated with or without specific inhibitors. L-Carnitine uptake in mature cells was sodium dependent and linear with time. Km and Vmax values for saturable uptake were 14.07 Ϯ 1.70 M and 26.3 Ϯ 0.80 pmol ⅐ mg protein Ϫ1 ⅐ 6 min Ϫ1 , respectively. L-carnitine uptake was inhibited (P Ͻ 0.05-0.01) by valproate and other organic cations. Anti-OCTN2 antibodies recognized a protein in the brush-border membrane (BBM) of Caco-2 cells with an apparent molecular mass of 60 kDa. The OCTN2 expression was confirmed by double immunostaining. Our results demonstrate that L-carnitine uptake in differentiated Caco-2 cells is primarily mediated by OCTN2, located on the BBM. intestine; brush-border membrane; organic cation transport; anti-OCTN2 antibodies; valproate.

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“…Mannitol and PEG are commonly used as nonmetabolizable markers for paracellular transport. Didanosine, 24,29 formycin B, 30,31 AZT, 32 proline, 33 phenylalanine, 34 and progesterone 35 have been reported as either stable or minimally metabolized in intestinal preparations.…”

Section: Materialssmentioning

confidence: 99%

Influence of the Microporous Substratum and Hydrodynamics on Resistances to Drug Transport in Cell Culture Systems: Calculation of Intrinsic Transport Parameters

Sinko

1997

Journal of Pharmaceutical Sciences

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Although cell culture models are increasingly used to study drug transport and metabolism, the influence of the substratum on the transport properties of the cell monolayer has not been studied in great detail. Furthermore, the use of effective (or apparent) permeabilities (Peff) assumes that the contribution of the microporous filter substratum and the aqueous boundary layer (ABL) to transport are negligible or are at least constant for a series of drugs. In the present study, the permeabilities of the substratum, ABL, and monolayer were obtained for a series of compounds at variable flow rates in side-by-side diffusion chambers. Comparisons of transport properties were made between cell monolayers grown on substrata made of polycarbonate (PC) and polyester (PE). All paracellular markers demonstrated a reduction in permeability and a corresponding increase in transepithelial electrical resistance (TEER) through PE-grown monolayers. The permeabilities of two carrier-mediated compounds, phenylalanine and proline, were 55% higher and 48% lower through PE-grown monolayers than through the PC-grown monolayers, respectively. The resistance to progesterone transport attributed to the PE and PC filters was large (71% and 27% of total resistance, respectively) at a flow rate of 20 mL/min, indicating that the monolayer was not the rate-limiting transport barrier. Therefore, for highly permeable compounds, reporting Peff has limited value since it is an indicator of the transport properties of the substratum rather than of the monolayer. These results demonstrate that substratum properties (e.g., membrane composition, pore size, etc.) significantly affect the barrier properties of the Caco-2 cell monolayer. The most probable mechanism is by the modulation of the functional expression of nutrient and ion transporters resulting in variable transcellular and paracellular transport properties. These results further demonstrate the importance of calculating intrinsic membrane transport parameters if the monolayer is not maintained as the rate-determining barrier in the transport experiment. Using higher flow rates and higher porosity substrata supports may help maintain the monolayer as the rate-limiting transport barrier.

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Proline uptake by monolayers of human intestinal absorptive (Caco-2) cells in vitro

Cited by 47 publications

References 35 publications

Transport of Pharmacologically Active Proline Derivatives by the Human Proton-Coupled Amino Acid Transporter hPAT1

Transport of Pharmacologically Active Proline Derivatives by the Human Proton-Coupled Amino Acid Transporter hPAT1

Expression and localization of organic cation/carnitine transporter OCTN2 in Caco-2 cells

Influence of the Microporous Substratum and Hydrodynamics on Resistances to Drug Transport in Cell Culture Systems: Calculation of Intrinsic Transport Parameters

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