title: Leakiness and size exclusion of paracellular channels in cultured epithelial cell monolayers-interlaboratory comparison.
abstract: 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.
authors.affiliation: pION INC, 5 Constitution Way, Woburn, Massachusetts 01801,USA. aavdeef@pion-inc.com
authors.forename: Alex
authors.initials: A
authors.lastname: Avdeef
mesh_terms: 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
chemical_list: D004364:Pharmaceutical Preparations