Glutamine reduces phorbol-12,13-dibutyrate-induced macromolecular hyperpermeability in HT-29Cl.19A intestinal cells

Background: Loss of mucosal integrity is associated with intestinal hyperpe rmeability, which may be inhibited by glutamine. The nature of this effect is unknown. The effect of glutamine on protein kinase C (PKC)-mediated hype rpermeability in HT-29Cl.19A intestinal cells was stud led. Methods: Conflu ent monolayers of HT-29Cl.19A cells were cultured on permeable filters and mounted in Ussing chambers for permeability studies. Apical to basolateral transepithelial permeability for intact horseradish peroxidase (HRP) was de termined. Phorbol-12,13-dibutyrate (PDB) was used to activate PKC-mediated hyperpermeability, and the effect of glutamine (0.6 mmol/L) was studied. Re sults: Two hours of PDB stimulation increased the HRP flux, reaching five t imes control values after 4 hours. Bilateral exposure to glutamine for 4 ho urs reduced PDB-induced hyperpermeability (37%). Preincubation with glutami ne 2 hours before PDB stimulation showed an earlier and greater effect (3 h ours, 43%; 4 hours, 50%). This bilateral effect of glutamine was mimicked b y separate apical exposure. Basolateral exposure alone had no effect. Concl usions: Glutamine rapidly reduced the PKC-mediated hyperpermeability for HR P in HT-29Cl.19A intestinal cells. The dependency on apical exposure sugges ts that glutamine may be more effective when delivered by the enteral route .