Table of Lectures - Society for Mycotoxin Research

May 14 th –16 th 2007, Fellbach P-63
Effects of deoxynivalenol on electrical properties across isolated
jejunal epithelium of laying hens are dose dependent
Wageha Awad, Josef Böhm, Ebrahim Razzazi-Fazeli, Jürgen Zentek
Institut für Ernährung, Veterinärmedizinische Universität Wien,
Veterinärplatz 1, A-1210 Vienna, Austria
Feeds contaminated with mycotoxins pose a health risk to animals and, as a consequence, may cause
big econimical losses due to lower efficacy of animal production. The most significant mycotoxins in contaminated
foods and feeds are Fusarium mycotoxins. Among the Fusarium toxins, deoxynivalenol (DON)
plays an important role, because it can occur in concentrations which are of toxicological relevance for
farm animals. The aim of the present studies was to evaluate the effects of DON on electrophysiological
parameters in laying hens’ jejunum mounted in Ussing chambers. In vitro studies were performed to
measure the effects of different luminal concentrations of DON (0.5, 1, 5, 10 µg/mL) on the electrical
tissue resistance (Rt) and electrogenic ion flux rates (short-circuit current, Isc) across the isolated gut
mucosa.
Materials and Methods: Lohmann Brown laying hens, 48 wk of age, were used in the present study.
Birds were killed by stunning and bleeding. Intestinal segments were immediately taken from the
proximal-jejunum. The epithelial sheets were mounted in modified Ussing chambers. Isolated epithelia
were incubated in D-glucose-free buffer mucosally and glucose-containing buffer serosally in Ussing
chambers for at least 20 min. Thereafter, 5 mL of Ringer solution on the luminal side were replaced by 5
mL of Ringer buffer containing different concentrations of DON (0, 2.5, 5, 25, 50 µg DON/5 mL of Ringer
solution). Furthermore, other experiments were performed to investigate the mechanisms of action of
DON. Amiloride (1 mmol/l), a specific inhibitor of Na + transport (Mall et al., 1998), was added to the luminal
side 15 min after addition of 5 µg DON/mL. In a second experiment, 5 mmol/L glucose was added
to the mucosal side. After 1 min incubation with glucose, DON or phlorizin (a specific inhibitor of SGLT1)
were added to the buffer solution. Data were compared by a paired t-test to evaluate the effects of both
substrates before and after their addition on Isc and Rt.
Results: The tissue resistance (317 ± 39 Ω·cm 2 , 325 ± 41 Ω·cm 2 , 371 ± 38 Ω·cm 2 ) was higher (p < 0.05)
in the tissues exposed to 1, 5, 10 µg DON/mL, respectively, compared with the basal values (229 ±-
17 Ω·cm 2 ). The addition of 1, 5, 10 µg DON/mL to the mucosal compartment was followed by an immediate
and steady decrease (p < 0.05) in Isc compared with the basal values. DON had a dose-dependent
effect on Isc, with a decrease of Isc to -12 ± 19, -20 ± 18 and -32 ± 11 µA/cm 2 , respectively, compared
with the basal values (42 ± 11 µA/cm 2 ). The Isc was not affected (p > 0.05) by the addition of amiloride
after incubation of tissues with DON, which did not have any further inhibitory effect. The addition of
DON or phlorizin to the mucosal solution after glucose addition decreased the current.
Conclusion: The main effect of DON was a dose-dependent decrease in the short-circuit current (Isc).
The decrease in Isc is apparently caused by the inhibitory effect of DON on Na + -transport; this is similar
to the effect of amiloride, an inhibitor of sodium ion transport. The addition of D-glucose on the luminal
side of the isolated mucosa increased Isc, and this effect was reversed by phlorizin and DON. This
finding indicates that the inhibition of Na + -transport and Na + -D-glucose co-transport are the important
mechanisms of DON toxicity in the intestine of laying hens.
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