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The present report demonstrates the effect of alpha toxin from Clostridium perfringens on electrophysiological indexes of jejunal mucosa from laying hens pretreated with inulin and N-acetyl-l-cysteine (ACC), a mucolytic agent. In a first set of experiments, the effect of alpha toxin with or without pretreatment with ACC on the electrophysiological parameters was determined when jejunal tissues from laying hens were mounted in Ussing chambers. The short-circuit current remained unchanged when alpha toxin was added mucosally in the tissues whether pretreated with ACC or not. The change in the transmural tissue conductance (DeltaGt) was higher (P = 0.18) after 90 min exposure of toxin independent of pretreament with ACC. The effect of alpha toxin on DeltaGt became significant (P < or = 0.05) after 120 min of incubation. In the second set of experiments, the effect of alpha toxin on the jejunal tissues preincubated with inulin (0.1%) was investigated. The effect of toxin was also time dependent, and DeltaGt became significantly higher (P < or = 0.05) after 120 min of incubation independent of preinubation with inulin. Inulin did not influence the DeltaGt during the experimental period when compared with control tissues. In conclusion, alpha toxin from C. perfringens can impair the intestinal mucosal barrier. The effect is obviously not dependent on the presence of a mucolytic agent nor can it be affected by direct addition of inulin under in vitro conditions. Whether there is an effect of inulin after long-term supplementation in feeding trials or it is due to fermentation bacterial metabolites remains an open question.