Toxic effects of carbendazim and n-butyl isocyanate, metabolites of the fungicide benomyl, on early development in the African clawed frog, Xenopus laevis.
We investigated the toxic effects of carbendazim and n-butyl isocyanate (BIC), metabolites of the fungicide benomyl, on development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of carbendazim (0-7 microM) and BIC (0-0.2 microM). LC(100) for carbendazim and BIC were 7 and 0.2 microM, respectively, and the corresponding LC(50), determined by probit analysis, were 5.606 and 0.135 microM. Exposure to carbendazim concentrations > or = 3 microM and BIC concentrations > or = 0.1 microM resulted in 10 different types of severe external malformation. Histological examinations revealed dysplasia of the brain, eyes, intestine, and somatic muscle, and swelling of the pronephric ducts. These phenomena were common in both test groups. The tissue-specific toxic effects were investigated with an animal cap assay. Neural tissues are normally induced at a high frequency by activin A, however, the induction of neural tissues was strongly inhibited by the addition of carbendazim. Conversely, the addition of BIC resulted in weak inhibition of neural tissues. Electron micrographs of animal cap explants revealed degeneration of cell junctions in the carbendazim-treated group, but not in the BIC-treated group. Numerous residual yolk platelets and mitochondrial degeneration were commonly observed in both test groups. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction and revealed that expression of the neural-specific marker neural cell adhesion molecule was more strongly inhibited in the carbendazim-treated group than in the BIC-treated group.
Yoon
Chun-Sik
CS
Department of Biology, College of Natural Sciences, Changwon National University, Changwon, Kyungnam, Korea.
Jin
Jung-Hyo
JH
Park
Joo-Hung
JH
Yeo
Chang-Yeol
CY
Kim
Song-Ja
SJ
Hwang
Yong-Gi
YG
Hong
Sung-Jin
SJ
Cheong
Seon-Woo
SW
D000818:Animals; D001542:Benomyl / Q000633:toxicity*; D001562:Benzimidazoles / Q000633:toxicity; D002219:Carbamates / Q000633:toxicity; D017931:DNA Primers; D004625:Embryo, Nonmammalian / Q000187:drug effects; D004781:Environmental Exposure; D005659:Fungicides, Industrial / Q000633:toxicity*; D017953:Isocyanates / Q000633:toxicity; D007928:Lethal Dose 50; D009420:Nervous System / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure; D012313:RNA / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000254:growth & development
D001562:Benzimidazoles; D002219:Carbamates; D017931:DNA Primers; D005659:Fungicides, Industrial; D017953:Isocyanates; D012313:RNA; C006698:carbendazim; D001542:Benomyl; C002509:butyl isocyanate