Is the amphibian X. laevis WEC a good alternative method to rodent WEC teratogenicity assay? The example of the three triazole derivative fungicides Triadimefon, Tebuconazole, Cyproconazole.

The aim of the present work is the assessment of teratogenic effects of three triazole-derived fungicides (Triadimefon, FON, Tebuconazole, TEBU, Cyproconazole, CYPRO) on rat and Xenopus laevis embryos cultured in vitro. Rat embryos, exposed to FON 31.25-250µM, CYPRO 31.25-62.5µM and to TEBU 62.5-250µM, showed specific malformations (fusions) at the level of the first and second branchial arches, with a concentration-dependent increase of severity of malformative pictures. After immunostaining, the ectomesenchyme has been identified as the target tissue. X. laevis larvae showed, at the same concentrations, specific malformations at the level of cartilaginous element derived from the first and second branchial arch ectomesenchyme. This work indicates the three tested triazoles as teratogenic both in rodents and in amphibian, inducing ectomesenchymal abnormalities, and suggests, at least for this class of molecules, the X. laevis method as adequate alternative model for teratogenic screening.

The agrochemical fungicide triadimefon induces abnormalities in Xenopus laevis embryos.

The dysmorphogenic activity of the triazole fungicide triadimefon (FON) has been evaluated using Xenopus laevis development. Embryos, exposed to 500 µM FON during early neurulation phases (stages 13-17, Nieuwkoop and Faber), were allowed to develop until stage 47. Larvae revealed serious craniofacial defects, bent forebrain, and abnormal hindbrain segmentation. CRABP and CYP26 (markers related to retinoic acid homeostasis) gene and protein expression and protein distribution have been evaluated at stage 17 and at the end of the branchial arch morphogenesis (stage 27) by real-time PCR, western blot and whole-mount immunostaining. A significant increase of CYP26 transcript has been observed at both embryonic stages. A co-localization of the two markers has been observed at the cephalic region. Embryos exposed to FON showed abnormal distribution of positive tissues. Due to the strict similarity of these results with those previously described in rodents, a FON-related alteration of mechanism conserved during vertebrate evolution is suggested.