Abstract
The permeability estimation from cell monolayer permeation data is usually based on 100% recovery assumption. However, poor recovery is often seen in such experiments in practice but often neglected in data interpretation. In the present study, the cellular retention kinetics during Caco-2 permeation experiments of three passively transported compounds, weakly basic propranolol [(±)-1-isopropylamino-3-(1-naphthyloxy)-2-propanol], weakly acidic ibuprofen [α-methyl-4-(isobutyl)phenylacetic acid], and neutral testosterone (17β-hydroxy-4-androsten-3-one), were determined. Furthermore, the effects of cellular retention kinetics on apparent permeability were evaluated, and the role of lysosomal sequestration in cellular retention of propranolol was explored. The cellular retention profiles were observed to be direction and concentration dependent, which may cause erroneous directionality and concentration dependence in permeability estimates. Furthermore, the lysosomal sequestration was demonstrated to contribute to the extent and kinetics of the cellular retention of propranolol.
Footnotes
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This work was supported by the National Technology Agency of Finland (TEKES).
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Portions of the data presented here appeared in abstract form as follows: Heikkinen AT, Korjamo T, and Mönkkönen J (2008) Cellular retention during permeation experiments: impact on permeability estimates and on P-glycoprotein mediated transport. In GPEN2008; 2008 Sept 10-12; Leuven, Belgium. Globalization of Pharmaceutics Education Network (GPEN), Inc., Lawrence, KS.
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doi:10.1124/jpet.108.145797.
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ABBREVIATIONS: A to B, apical to basal direction; B to A, basal to apical direction; Papi, permeability coefficient through barrier between apical and cytosolic compartments (unstirred water layer and cell membrane); Pbaso, permeability coefficient through barriers between basal and cytosolic compartments (unstirred water layer, filter support, and cell membrane); K, apparent cell-buffer distribution coefficient; Kmax and Kmin, higher and lower limits for apparent cell-buffer distribution coefficient, respectively; Q12 and Q21, first-order rate coefficients for mass transfer from cytosol to lysosome and lysosome to cytosol, respectively; Papp,sink, estimated apparent permeability through cell monolayer assuming sink conditions; Papp,nonsink, estimated apparent permeability through cell monolayer without sink condition assumption; Papp, apparent permeability through cell monolayer.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material. - Received September 18, 2008.
- Accepted December 15, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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Kinetics of Cellular Retention during Caco-2 Permeation Experiments: Role of Lysosomal Sequestration and Impact on Permeability Estimates
