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Evaluation of aflatoxin B1 embryotoxicity using the frog embryo teratogenesis assay-Xenopus and bio-activation with microsome activation systems.

Vismara C, Caloni F

Department of Biology, University of Milan, Italy. claudio.vismara@unimi.it

BACKGROUND: Aflatoxins are a group of mycotoxins produced by Aspergillus, A. flavus, and A. parasiticus. Aflatoxin B1 (AFB1) should be a strong teratogen in hamsters, but its effect in rats is equivocal and extremely limited in mice. Therefore, the AFB1 embryotoxic potential in mammals remains unclear. METHODS: Little is known about the AFB1 effects on amphibians, therefore its embryotoxic potential was evaluated using the frog embryo teratogenesis assay-Xenopus (FETAX). X. laevis blastulae were exposed to: 1) positive controls for bio-activation (4 g/L cyclophosphamide monohydrate, Cy, and 4 g/L Cy+30 mg/L MAS-rat; 4 g/L Cy+30 mg/L MAS-human); 2) positive controls for MAS (30 mg/L MAS-rat and 30 mg/L MAS-human); 3) exposed groups to AFB1 (1 mg/L AFB1); and 4) AFB1 bio-activation (1 mg/L AFB1+30 mg/L MAS-rat and 1 mg/L AFB1 +30 mg/L MAS-human). RESULTS: In MAS-rat and human, Cy did not induce a statistically significant increase of mortality and malformed larvae percentage, but when bio-activated Cy increased the percentage of mortality. Instead, MAS-rat and human alone did not show any increase of mortality and malformed larvae percentages. When bio-activated by MAS-rat and human, AFB1 increased significantly both the mortality and malformed larvae percentages. The malformed larvae were mainly plurimalformed, i.e., affected by generalized edema, abnormal gut coiling, and microphthalmia. CONCLUSIONS: This research shows that AFB1 alone is not embryotoxic but, when bio-activated with MAS-rat or MAS-human the percentage of mortality and malformed larvae increased significantly. These results also show that AFB1 must be bio-activated to exert its embryotoxic effects.

Published 3 July 2007 in Birth Defects Res B Dev Reprod Toxicol, 80(3): 183-7.
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