Leakiness and size exclusion of paracellular channels in cultured epithelial cell monolayers-interlaboratory comparison.
OBJECTIVE
To determine and compare the paracellular characteristics of permeability (Papp) of Caco (-2), MDCK, and 2/4/A1 cell lines.


METHODS
The Papp data from 14 studies were analyzed by weighted nonlinear regression in terms of the paracellular parameters: porosity-pathlength (epsilon/delta), pore radius (R), and electrostatic potential drop (deltaphi). Aqueous diffusivities, Daq, for the analysis, were empirically determined. The required hydrodynamic radii, rHYD, were estimated without knowledge of compound density. Mannitol iso-paracellular profiles allowed comparisons of "leakiness" across labs.


RESULTS
Daq (37 degreeC) was predicted as 9.9x10(-5) MW(-0.453); rHYD=(0.92+21.8 MW(-1))xrSE, where rSE is the Stokes-Einstein radius. Values of pore radius ranged from 4.0(+/-0.1) to 18(+/-3) A, with the 2/4/A1 indicating the largest pores. The epsilon/delta capacity factor ranged from 0.2 (+/-0.1) to 69 (+/-5) cm(-1), with most values <1.5 cm(-1). The average potential drop for Caco-2 models was deltaphi(wt avg) Caco(-2)=(-43)+/-20 mV. The paracellular model predicted measured log Papp values with pooled r2=0.93 and s=0.17 (n=108).


CONCLUSIONS
R and epsilon/delta are negatively correlated to a large extent. Papp can be rate-limited by either factor, with a wide range of possible combinations still indicating nearly constant leakiness for a given marker.
Avdeef
Alex
A
pION INC, 5 Constitution Way, Woburn, Massachusetts 01801,USA. aavdeef@pion-inc.com
D000818:Animals; D018938:Caco-2 Cells; D002460:Cell Line; D002463:Cell Membrane Permeability; D004058:Diffusion; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D004364:Pharmaceutical Preparations / Q000737:chemistry; D010599:Pharmacokinetics
D004364:Pharmaceutical Preparations