Mixture effect of two agrochemical antifungal triazoles (triadimefon and cyproconazole) in two different alternative developmental animal models (WEC and FETAX)

Azole fungicides are described as teratogenic in different animal models, inducing cranio-facial defects. The aim of the present work is to evaluate the teratogenic potential of two triazole-derived fungicides (triadimefon, FON, cyproconazole, CYPRO) alone or in a mixed solution by using two different alternative animal models (rat postimplantation Whole Embryo Culture- WEC and Frog Embryo Teratogenesis Assay: Xenopus- FETAX). On the basis of the morphological and molecular interclasses similarities at the phylotypic stage, low vertebrate animal models have been proposed as alternative to mammals in assessing the developmental toxicity of xenobiotics. Rat embryos were exposed during the whole culture period (from early neurulation till phylotypic stage) to 7.8-250µM of two agrochemical triazoles (FON and CYPRO) alone, or to their mixture (FON 7.8µM plus CYPRO 7.8µM). At the end of the culture period, embryos were morphologically examined and immunostained to evaluate neural crest cell (NCC) migration. Xenopus laevis embryos were exposed during early neurulation stages to FON and CYPRO alone (3.9-250µM), or to their mixtures (FON 3.9µM plus CYPRO 3.9µM). At the end of the exposure period, embryos were washed and allowed to reach the phylotypic stage (to evaluate neural crest cell migration) or the tadpole stage (to evaluate the craniofacial morphology). In both animal models, FON and CYPRO were teratogenic and showed a clear mixture effect (the mixture of no effect levels resulted effective in inducing teratogenic effects, suggesting that the teratogenic mechanism is common for the two molecules). The evidence that similar results were obtained both in rat and X. laevis embryos, indicates X. laevis as an adequate alternative animal model for teratogenic screening of mixtures of xenobiotics.