BACKGROUND AND AIMS: Intact protein absorption is thought to be a causative factor in several intestinal diseases, such as food allergy, celiac disease and inflammatory bowel disease. However, the mechanism remains unclear. The aim of this study was to characterize a novel signal transduction pathway via which heat stress compromises intestinal epithelial barrier function. METHODS: Heat stress was carried out by exposing confluent human intestinal epithelial cell line T84 cell monolayers to designated temperatures (37-43 degrees C) for 1 h. Transepithelial electric resistance (TER) and permeability to horseradish peroxidase (HRP, molecular weight = 44 000) were used as indicators to assess the intestinal epithelial barrier function. Phosphorylated myosin light chain (MLC), MLC kinase (MLCK) and protein kinase C (PKC) protein of the T84 cells were evaluated in order to identify the signal transduction pathway in the course of heat stress-induced intestinal epithelial barrier dysfunctions. RESULTS: The results showed that exposure to heat stress significantly increased intact protein transport across the intestinal epithelial monolayer; the amount of phospho-PKC, phospho-MLCK and phospho-MLC proteins in T84 cells decreased significantly at 41 degrees C and 43 degrees C although they increased at 39 degrees C. The heat stress-induced T84 monolayer barrier dysfunction was inhibited by pretreatment with PKC inhibitor, MLCK inhibitor, or HSP70. CONCLUSION: Heat stress can induce intestinal epithelial barrier dysfunction via the PKC and MLC signal transduction pathway.