Butafenacil: A positive control for identifying anemia- and variegate porphyria-inducing chemicals
2015
Leet, Jessica K. | Hipszer, Rachel A. | Volz, David C.
Butafenacil is an herbicide that inhibits protoporphyrinogen oxidase (PPOX), an enzyme that catalyzes oxidation of protoporphyrinogen IX to protoporphyrin IX during chlorophyll and heme biosynthesis. Based on a high-content screen, we previously identified butafenacil as a potent inducer of anemia in zebrafish embryos. Therefore, the objective of this study was to begin investigating the utility of butafenacil as a positive control for identifying anemia- and variegate porphyria-inducing chemicals. Static exposure to butafenacil from 5 to 72h post-fertilization (hpf) in glass beakers resulted in a concentration-dependent decrease in arterial circulation at low micromolar concentrations. At 72hpf, the magnitude of butafenacil-induced anemia was similar when embryos were exposed in the presence or absence of light, whereas protoporphyrin accumulation and acute toxicity were significantly lower or absent when embryos were exposed under dark conditions. To identify sensitive developmental windows, we treated embryos to butafenacil from 5, 10, 24, or 48hpf to 72hpf in the presence of light, and found that anemia and protoporphyrin accumulation were present at 72hpf following initiation of exposure at 5 and 10hpf. On the contrary, protoporphyrin accumulation – but not anemia – was present following initiation of exposure at 24hpf. Lastly, protoporphyrin accumulation at 72hpf after exposure from 24 to 48hpf suggests that protoporphyrin was not eliminated over a 24-h recovery period. Collectively, our data suggests that butafenacil may be a reliable positive control for identifying anemia- and variegate porphyria-inducing chemicals.
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