Epithelial barrier function and ion transport was studied in coeliac sprue using a miniaturised Ussing device for measurements on diagnostic aspiration biopsy specimens from the jejunum of untreated or gluten free nourished sprue patients, or from healthy controls. Pure epithelial resistance (Re) indicating epithelial barrier function was determined by transmural alternating current impedance analysis. It was reduced by 56% in acute sprue mean (SEM) (9 (1) omega.cm2) compared with controls (20(2) omega.cm2). In gluten free nourished sprue patients Re was only partly recovered (15 (1) omega.cm2). Subepithelial resistance (Rsub) was also changed from 28 (1) omega.cm2- in control to 17 (1) omega.cm2 in acute sprue because of the change in mucosal architecture, but was unchanged in gluten free nourished sprue patients (29 (4) omega.cm2). In acute sprue, unidirectional Na+ and Cl- fluxes were increased in both directions as a consequence of the decreased resistance. However, short circuit current (ISC) as well as Na+ and Cl- net fluxes were not significantly different from control. Subsequently, the electrogenic Cl- secretory system was investigated. After maximal stimulation with theophylline and prostaglandin E1, a Cl(-)-dependent increase in ISC was obtained in the sprue mucosa and control jejunum. It showed saturation characteristics and was blockable by serosal bumetanide. When compared with control, neither Km nor Vmax of this electrogenic Cl- secretion was significantly changed in coeliac sprue. In conclusion, a miniaturised Ussing device was used for transport measurements on intestinal biopsy specimens. In acute coeliac disease, the epithelial barrier of the jejunum was seriously disturbed. The active electrogenic Cl- secretory transport system was present in the sprue mucosa, but was not activated in the Ussing chamber in vitro when compared with control jejunum.