The Toxicologist - Society of Toxicology

was an increase in the number of terminal end buds in males (P E1. To determine whether transcriptional regulation of VTG
correlated with protein expression, quantitative real-time PCR was performed.
mRNA was collected from cryopreserved hepatocytes treated for 24 hours with the
same doses of reference chemicals. VTG gene expression correlated well with protein
expression, ranking the compounds similarly. In addition, the negative control
corticosterone showed no increase in gene expression at any dose, indicating that
this is a sensitive, yet specific endpoint. These studies demonstrate both ELISA and
transcription-based methods can be used with cryopreserved trout hepatocytes for
screening chemicals for potential estrogenic effects, enabling greater access to this
model system and potentially improving the turn-around time for generating results
through detection of VTG mRNA levels.
102 Permethrin Does Not Have Endocrine Disrupting Properties
As Evaluated by the US EPA’s Endocrine Disruptor Screening
Program (EDSP) In Vivo Assays.
L. Zorrilla 1 , S. J. Borghoff 1 and T. G. Osimitz 2 . 1 Integrated Laboratory Systems,
Inc, Durham, NC; 2 Science Strategies, Charlottesville, VA.
Permethrin, a pyrethroid insecticide, was evaluated for potential endocrine activity
in 3 of 4 in vivo US EPA EDSP assays. The maximum tolerated dose (MTD) of
permethrin used in these assays was selected based on the results of dose range finding
studies. Sprague Dawley rats were administered permethrin in corn oil by oral
gavage for 10 (Hershberger Bioassay, OPPTS 890.1400, castrated model), 21/22