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Impact of extracellular protein binding on active drug transport across Caco-2 cells
Uppsala University, Medicinska vetenskapsområdet, Faculty of Pharmacy, Department of Pharmacy.
Article in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-93111OAI: oai:DiVA.org:uu-93111DiVA: diva2:166489
Available from: 2005-05-12 Created: 2005-05-12Bibliographically approved
In thesis
1. Refined in vitro Models for Prediction of Intestinal Drug Transport: Role of pH and Extracellular Additives in the Caco-2 Cell Model
Open this publication in new window or tab >>Refined in vitro Models for Prediction of Intestinal Drug Transport: Role of pH and Extracellular Additives in the Caco-2 Cell Model
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drug transport across the intestinal epithelium is roughly predicted from permeability values obtained from Caco-2 cell monolayers. This thesis examines the important role of pH and extracellular additives for increasing the reliability and predictivity of the in vitro screening system, Caco-2.

It was shown that the passive transport of ionizable compounds may be biased by a false efflux or uptake component, when applying a physiological pH-gradient across the membrane. pH also affected the amount of compound available at the transporter-binding site. Therefore, pH dependence should be considered in studies of such compounds and of drug-drug interactions involving efflux transporters. It was also shown that proton-dependent apical uptake or basolateral efflux should be studied both with and without a pH gradient over the whole monolayers.

The two extracellular additives, bovine serum albumin (BSA) and the solubilizing agent, Cremophor® EL, also influenced Caco-2 permeabilities. BSA applied to the receiver side increases, and to the donor side decreases drug permeation according to the drug’s protein binding capacity. Thus, the absorptive transport for both passive and active compounds is favoured, giving a physiologically sound improvement of the Caco-2 cell model. Inclusion of BSA increased both the predictivity and quality of permeability studies, particularly of highly lipophilic, BCS class II compounds. Passive and active transport processes could also be distinguished after accounting for unbound concentrations. The overall effect of Cremophor® EL on the permeability to a drug was compound-specific and probably dependent on micellar incorporation. Cremophor® EL can therefore not be recommended.

Neither pH nor BSA affect the functionality of transporters such as P-glycoprotein. However, efflux ratios of ionizable or protein bound drugs are altered in the presence of a pH-gradient or BSA, indicating that an experimental system without protein or pH gradient can over- or underestimate active and passive efflux in drug transport.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 83 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 14
Pharmacy, Caco-2 cells, membrane permeability, drug permeation, drug efflux ratios, drug uptake ratios, Cremophor EL, bovine serum albumin, pH-dependent permeability, drug transport, FARMACI
National Category
Pharmaceutical Sciences
urn:nbn:se:uu:diva-5814 (URN)91-554-6262-6 (ISBN)
Public defence
2005-06-02, B22, Uppsala Biomediciniska centrum, Uppsala, 13:15
Available from: 2005-05-12 Created: 2005-05-12 Last updated: 2011-09-19Bibliographically approved

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