Toxoplasma gondii: changes of transepithelial ion transport in infected HT29/B6 cell monolayers

An in vitro system was established to study the effect of coccidian parasites on ion transport systems in epithelial tissues using HT29/B6, a human colon carcinoma cell line, and Toxoplasma gondii as a model parasite. Ion transport was measured in perfusion chambers 5, 10 and 15 h post-infection using monolayers in which approximately 30% of the cells were parasitized. The infection had rapid effects on the conductance and unidirectional chloride fluxes of infected cell monolayers, which were two to three times higher than those of uninfected HT29/B6 cell monolayers throughout the observation period. However, the chloride net fluxes and short-circuit current were unaffected by the parasites, while the decrease of chloride seromucosal fluxes and conductance after addition of bumetanide were affected by the infection. The unidirectional mannitol fluxes, which correspond with water motion through paracellular pathways, were increased in infected HT29/B6 cell monolayers.