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Toxicity Screening of the ToxCast Phase II Chemical Library Using a Zebrafish Developmental Assay (SOT)
Citation:
Mosher, S., K. Houck, S. Frady, R. Judson, J. Wambaugh, D. Reif, AND S. Padilla. Toxicity Screening of the ToxCast Phase II Chemical Library Using a Zebrafish Developmental Assay (SOT). Presented at SOT 2014 Annual Conference, Phoenix, AZ, March 23 - 27, 2014. https://doi.org/10.23645/epacomptox.5193253
Impact/Purpose:
As part of the chemical screening and prioritization research program of the US EPA, the ToxCast Phase II chemicals were assessed using a vertebrate screen for developmental toxicity. Zebrafish embryos (Danio rerio) were exposed in 96-well plates from late-blastula stage (6hr postfertilization, pf) through day 5pf (1-2 days post-hatch).
Description:
As part of the chemical screening and prioritization research program of the US EPA, the ToxCast Phase II chemicals were assessed using a vertebrate screen for developmental toxicity. Zebrafish embryos (Danio rerio) were exposed in 96-well plates from late-blastula stage (6hr postfertilization, pf) through day 5pf (1-2 days post-hatch). All exposures were by immersion and renewed daily. The 700 chemicals included food additives, consumer use product ingredients, pesticides, failed pharmaceuticals, and “green” plasticizers (http://epa.gov/ncct/toxcast/chemicals.html). Intra- and inter-plate replicates were included for quality control. Developmental toxicity was initially assessed using a single nominal concentration of 80 µM: positives and a selection of negatives were confirmed by concentration-response determinations. On day 5pf, larvae were moved from exposure solution to a control solution without chemical, and on day 6pf were assessed for overt toxicity (i.e., death, non-hatching and dysmorphology; n=4 embryos per chemical). Dysmorphology was a combined score using both in-life observation and brightfield, high-content image analysis. Overt toxicity was noted with 46% of the chemicals tested, compared to 62% positive chemicals when the ToxCast Phase I library, consisting of mostly pesticide active ingredients, was previously tested. As with the Phase I library, the octanol-water partition coefficient (logkow ) of the Phase II library chemicals was positively correlated with overt toxicity: there were 18% positive chemicals with logkow <0; 41% positive chemicals with logkow of 0 to 4; and 67% positive chemicals with a logkow >4. All chemicals positive at the single concentration were further assessed for potency using a Dose-Response Study (8-point, semi-log concentration curve: n=3 embryos per concentration). These data demonstrate the utility of zebrafish in medium-throughput chemical testing programs for detection of adverse developmental outcomes. This abstract may not necessarily reflect official Agency policy.
URLs/Downloads:
DOI: Toxicity Screening of the ToxCast Phase II Chemical Library Using a Zebrafish Developmental Assay (SOT)
MOSHER ET AL 2014 SOT ABSTRACT 12-12-13_KAH.PDF (PDF, NA pp, 69.929 KB, about PDF)
MOSHER ET AL _SOT_POSTER_FINAL.PDF (PDF, NA pp, 740.818 KB, about PDF)