The Toxicologist - Society of Toxicology

diated transcriptional response of all three ERs as compared to the two tandem
EREs. PPT is not a specific agonist for the LMB ERα, as it also activates ERβ, and
DPN was shown to activate the ERβs as well as the ERα. As expected, pp’-DDE
and BPA were weak agonists of all three receptors. Dieldrin appears to be a more
specific agonist of ERα, as it is not very efficacious in activating either ERβb or
ERβa. The three LMB ERs showed different sensitivities to ICI 182,780, but at
high concentrations (>5μM) it was able to completely inhibit the E2-mediated activation
of all three ERs. Tissue slices from LMB livers will be used to test the effects
of the above mentioned compounds on vtg synthesis.
2358 IMPACT OF OSRI ON ANIMAL USE AND SCREENING
BURDEN FOR TIER I EDSP COMPLIANCE.
S. C. Gehen 1 and W. R. Jones 2 . 1 Dow AgroSciences, LLC, Indianapolis, IN and
2 CropLife America, Washington, DC.
In response to provisions of the Food Quality Protection Act (FQPA), EPA developed
the endocrine disruptor screening program (EDSP) with the intent to identify
chemicals that might interact with estrogen, androgen, or thyroid systems. In late
2009, EDSP was implemented with receipt of testing orders for the chemicals on
the first screening list, the majority being pesticide active ingredients. According to
FQPA language and EPA policy, registrants can utilize existing toxicology information-
or other scientifically relevant information (OSRI) - in lieu of generating new
data for some or all tier I assays. This policy is especially noteworthy for pesticides
where existing legislation mandates a comprehensive registration package of toxicology
studies, several which assess endocrine-sensitive parameters. To evaluate the
impact of OSRI on animal use and overall burden of endocrine screening, a retrospective
analysis of registrant and EPA responses was conducted. Of the 58 individual
pesticide registrants and consortia receiving testing orders, about 10% opted to
voluntary cancel their respective EPA registration. Of those remaining, the degree
to which registrants utilized OSRI was variable with 34% submitting OSRI for all
11 tier I assays, 47% for a sub-set of tier I assays, and 9% choosing to conduct all
11 assays. Registrants cited or submitted OSRI for a total of 211 (61%) in vivo
EDSP studies; these responses ranged from 76% citing OSRI for the male pubertal
assay to just 47% for the fish short-term reproduction assay. Of the first 5 test order
responses published by EPA, registrants cited OSRI for 14 out of a possible 30 in
vivo assays; however, none of these data-sets were considered sufficient by EPA to
satisfy the test order, thus indicating that new in vivo studies would be required.
Understanding the agency’s rationale for accepting or rejecting data submitted as
OSRI will be increasingly important as this rationale directly affects animal use and
the overall resource burden of the EDSP program.
2359 ORAL EXPOSURE TO BISPHENOL A IMPACTS
ELECTROCARDIOGRAPHIC PARAMETERS IN CD-1
MICE.
C. B. Lo, T. B. McCutchan, E. L. Kendig and S. M. Belcher. Pharmacology,
University of Cincinnati, Cincinnati, OH.
Bisphenol A (BPA) is an estrogenic endocrine disrupting chemical that is prevalent
in the environment. Humans are exposed to significant amounts of BPA from the
consumption of contaminated foods, beverages and other poorly defined routes.
Our research has demonstrated that BPA can affect the cardiovascular system by altering
intracellular Ca2+ handling in myocytes causing altered EC coupling and arrhythmias.
The aim of this study was to determine whether oral exposure to estradiol
or BPA can influence normal electrical function and rhythm of the heart in live
CD1 mice. Male and female CD-1 mice were randomly paired following a two
week pre-treatment period during which time animals were exposed to control diet
or diet containing BPA (0.03, 0.3, 3, 30, and 300 ppm) or 17α-ethinyl estradiol
(EE; 0.0001, 0.001, and 0.01 ppm). Treatments were continued through the life of
breeders (F0) and offspring (F1). Electrocardiogram (ECG) data was collected and
analyzed from conscious and unrestrained mice at different time points prior to
mating, during pregnancy, and during offspring development. Because levels of endogenous
estrogen vary during the estrous cycle, the stage of estrous at time of
recording was determined. No significant differences in heart rate or other ECG
parameters were observed during estrous in the control group. Dietary exposure to
BPA (0.03 ppm and 0.3 ppm) and EE (0.01 ppm) caused significant effects on cardiovascular
function during diestrus and estrus in CD-1 mice. The most efficacious
dose of BPA was 0.3 ppm, while no effects have been observed at 30.0 ppm BPA. In
F0 females 0.03 ppm BPA significantly increased heart rate and heart rate variability
was suppressed in males. In the offspring (F0), BPA (0.03 ppm and 0.3 ppm)
and EE caused significant effects on cardiovascular function during diestrus and estrus.
For these endpoints the most efficacious dose of BPA was 0.3 ppm, with no effects
observed at 30.0 ppm BPA.
2360 INTEGRATING HUMAN AND TOXICOLOGICAL
EVIDENCE TO UNDERSTAND PCB EFFECTS ON THE
DEVELOPING BRAIN.
F. Parham 1 , A. Wise 2 , D. A. Axelrad 3 , K. Z. Guyton 3 , C. J. Portier 4 , L. Zeise 5 ,
R. T. Zoeller 6 and T. J. Woodruff 2 . 1 National Institute for Environmental Health
Science, Research Triangle Park, NC, 2 University of California, San Francisco, CA,
3 U.S. EPA, Washington, DC, 4 Centers for Disease Control and Prevention, Atlanta,
GA, 5 California EPA, Oakland, CA and 6 University of Massachusetts, Amherst, MA.
We reviewed the relationships between chemical exposure, early biological disturbances,
and subsequent overt health effects for thyroid hormone disruptions in a
case study approach. Thyroid hormones (TH; thyroxine, T4 and triiodothyrine,
T3) are essential for normal brain development and for normal physiological controls
in adults. Mechanistic, laboratory animal, and human studies indicate that
TH disruption during the prenatal period can cause permanent cognitive and neurobehavioral
deficits. The quantitative relationships between TH disruption due to
chemical exposures and overt disease were analyzed for polychlorinated biphenyls
(PCBs). PCBs were chosen because sufficient animal and human data exist to
model and compare body burdens, TH disruption and health decrements. We
modeled three relationships following a review of 13 epidemiologic studies, applying
meta-analysis where appropriate: 1) chemical exposures and TH changes; 2)
pregnancy TH changes and neurodevelopmental outcomes of children; and 3) prenatal
PCB exposures and neurodevelopmental outcomes of children. Using data
from four chronic PCB studies in rats conducted by the National Toxicology
Program, we developed a low-dose linear model of PCB body burdens and T4 (free
and total) decrements, accounting for 35 PCB congeners. A human extrapolation
of the animal findings generally under-predicted the dose-response estimated from
human studies. This quantitative analysis can inform approaches for evaluating
human health consequences of exposures to multiple chemicals that exert thyroid
toxicity.
Disclaimer: The views expressed are those of the authors and do not necessarily represent
the views and/or policies of the US EPA.
2361 GENISTEIN NEGATES THE INHIBITORY EFFECTS OF
LETROZOLE ON AROMATASE RELATED TO
MALIGNANT, BUT NOT HEALTHY BREAST TISSUE.
M. van Duursen 1 , E. de Morree 1 , S. Nijmeijer 1 , P. de Jong 2 and M. van den
Berg 1 . 1 Institute for Risk Assessment Sciences, Utrecht University, Utrecht, Netherlands
and 2 Department of Internal Medicine, St. Antonius Hospital, Nieuwegein,
Netherlands.
Aromatase (cytochrome P450 19, CYP19) catalyzes the conversion of androgens
into estrogens. Especially in post-menopausal women, estrogen production in
breast tissue by CYP19 becomes a major site of hormone production. In healthy
breast adipose fibroblasts (BAF), CYP19 expression is low and is mainly driven by
promoter I.4. In fibroblasts surrounding a tumor, a promoter switch to PI.3/II
takes place and CYP19 expression is elevated 3-4-fold. This makes this enzyme an
important target for estrogen-dependent breast cancer treatment by aromatase inhibitors,
such as letrozole (LET). Breast cancer treatment often results in sudden
onset of menopausal symptoms and many women seek for alternative therapies to
treat these symptoms. A commonly used treatment is the soy-isoflavone genistein
(GEN). In this study, the potential interaction between LET and GEN on CYP19
was studied. In healthy primary human BAFs, PI.4-driven CYP19 expression was
increased 45-fold by its stimulant dexamethasone. Expression of PI.3/II-driven aromatase
was low in BAFs and only increased 7-fold by the stimulant PGE2. GEN
did not affect CYP19 expression in BAFs. In contrast, in human adrenocorticocarcinoma
H295R cells, that express PI.3/II-driven CYP19, GEN concentration-dependently
induced aromatase activity (EC50=26 μM) and expression. LET inhibited
CYP19 activity in H295R cells with an IC50 value of 0.2 μM. Co-incubation
with GEN resulted in a concentration-dependent negation of CYP19 inhibition by
LET through increased CYP19 expression. This interaction did not affect the
EC50 of genistein, nor did it alter the IC50 of LET. These data indicate that the actions
of GEN on CYP19 appear to be restricted to PI.3/II-driven CYP19 that can
be found in BAFs surrounding a tumor. Therefore, the use of GEN by women undergoing
breast cancer treatment with LET should be considered with care.
2362 EFFECTS OF REDUCED-PHYTOESTROGEN DIETS ON
DEVELOPMENT OF CD1 AND C57BL/6N MICE.
E. L. Kendig, S. M. Christie, D. R. Buesing, C. K. Cookman, R. B. Gear, C.
B. Lo and S. M. Belcher. Pharmacology, University of Cincinnati, Cincinnati, OH.
Endocrine disrupting chemicals (EDC) are chemicals that can affect endocrine-dependent
development and function. These chemicals are prevalent in the environment
and exhibit a variety of biological effects. Because of limited ability to replicate
results from some animal studies controversy surrounds the possible harmful
SOT 2011 ANNUAL MEETING 507