Fig. 4. Comparison of claudin protein expression profiles in MDCK II and MDCK C7 cells. Comparative immunoblotting was performed to determine whether the difference in TER and pore number between MDCK II and C7 cell lines could result from different claudin expression profiles. Duplicate cell monolayer filters that were used for immunofluorescent analysis (Fig. 3) were processed for immunoblots with a panel of antibodies against claudins and other junction proteins to compare relative protein levels; quantification was performed using Licor Odyssey software. Levels in MDCK C7 cells are presented relative to MDCK II levels. Most claudins, ZO-1, occludin and E-cadherin are expressed at similar levels, whereas, in C7 cells, claudin-2 is much less prevalent and claudin-4 much more prevalent.