Acetaminophen changes paracellular transport activity through regulation of the tight junction protein in an intestinal barrier model

permeability of the small molecules Lucifer Yellow (ca. 520 Da) and FITC-dextran (3– 5k Da) but not of large molecules (40 kDa FITC-dextran). The tight junction protein ZO-1 and its tyrosine phosphorylation were upregulated after 24 h treatment with APAP. Conclusions Tight junction proteins play an important role in maintaining the intestinal barrier function. We assume that APAP affects the paracellular transport pathway through disassembly of the tight junction. We suppose that APAP leads to remodelling of the tight junction protein ZO-1 through changes in the level of protein expression and in tyrosine phosphorylation. APAP may reduce the bioavailability of co-administered substances through remodelling the tight junction by regulating ZO-1 and its tyrosine phosphorylation. As a result, the paracellular transport activity for small molecules is decreased as is net intestinal absorption.