Monograph on the Potential Human Reproductive and ... - OEHHA

222 CHAPIN ET AL.
Table 56
Anti-Androgenicity Studies of Bisphenol A in Cells Transfected With Androgen Receptor Reporter
Reference androgen Bisphenol A median inhibitory
Cell type concentration (nM) concentration (IC50) mM [mg/L] Reference
Human prostate
adenocarcinoma
R1881 0.1 7 [1.6] Paris et al. (2002)
Chinese hamster ovary R1881 0.1 19.6 [4.5] Roy et al. (2005)
Yeast Testosterone 10 1.8 [0.4] Lee et al. (2003a)
Yeast Dihydrotestosterone 1.25 [0.5] Sohoni and Sumpter (1998)
Monkey kidney Dihydrotestosterone 1 0.746 [0.2] Xu et al. (2005)
Monkey kidney Dihydrotestosterone 1 2.14 [0.5] Sun et al. (2006)
Mouse fibroblast Dihydrotestosterone 0.01 4.3 [1.0] Kitamura et al. (2005)
Human hepatoma Dihydrotestosterone 100 No anti-androgenic activity Gaido et al. (2000)
a Estimated from a graph.
rapidly after exposure to bisphenol and 17b-estradiol
concentrations of 10 -10 M through a non-ER-mediated
mechanism (Walsh et al., 2005).
Recently, bisphenol A was identified as competitor to
17b-estradiol for binding to the GPR30 receptor; a novel
seven-transmembrane receptor that mediates nongenomic
estrogen actions to upregulate adenylyl cyclase
and MAPK activities (Thomas and Dong, 2006). Similar
to findings reported previously with nuclear estrogen
receptors and membrane estrogen receptors, bisphenol A
was identified as a relatively effective competitor of 17bestradiol
binding, with relative binding affinities of 2.8%
that of the natural estradiol ligand and an IC50 of
630 x 10-9 M. Bisphenol A, at a concentration of
200 nM significantly increased cAMP levels in transfected
cells 30 min after compound addition.
Bisphenol A has been found to bind estrogen-related
receptor g, a nuclear receptor with no known natural
ligand that shows little affinity for 17b-estradiol (Takayanagi
et al., 2006). Estrogen-receptor g demonstrates
high constitutive activity that is maintained by bisphenol
A in the presence of 4-hydroxytamoxifen, which otherwise
blocks nuclear ER activity. This observation led to
the suggestion that bisphenol A may maintain estrogenrelated
receptor g activity in the presence of a yet-to-beidentified
natural antagonist and that cross talk between
the estrogen-related receptor and ER systems could be
responsible for the estrogenic activity of bisphenol A in
spite of low binding affinity for ERa and b (Takayanagi
et al., 2006).
In addition to the studies reviewed for this section,
there are studies in which the putative estrogenicity of
environmental samples or synthetic products were
evaluated using one or another assay. For example, Olea
et al. (1996) evaluated resin-based dental composites in
an MCF-7 culture system. The response of the system
was attributed to the bisphenol and its methacrylate
detected in the composites, but bisphenol A was not
specifically tested. These articles were not reviewed for
this section.
2.2.3 Androgen activity. Transfected cell-based
assays have not identified bisphenol A as having
androgenic activity (Sohoni and Sumpter, 1998; Gaido
et al., 2000; Kitamura et al., 2005; Xu et al., 2005).
However, bisphenol A is mitogenic in cultured human
prostate carcinoma cells at a concentration of 1 nM
(Wetherill, 2002). Based on stimulated cell growth in this
system, the potency of bisphenol A is about 5% that of
2 a
dihydrotestosterone [estimated from a graph]. This
bisphenol A activity was shown to be mediated by
interaction with a mutant tumor-derived androgen
receptor called AR-T877A. Anti-androgenic activity has
been demonstrated using cells transfected with androgen
receptor reporting systems (Table 56). The anti-androgenic
activity of bisphenol A is expressed as the
concentration needed to halve the androgen reporter
response to a reference androgen. Studies in transfected
cells have shown that bisphenol A interferes with the
binding of dihydrotestosterone to the androgen receptor,
interferes with translocation of the liganded receptor to
the nucleus, and prevents transactivation at the androgen-response
element (Lee et al., 2003a).
Kim et al. (2002a) conducted a Hershberger assay to
determine the effects of bisphenol A exposure on
reproductive organs of rats. Sprague–Dawley rats were
fed PMI Certified Rodent LabDiet and housed in
polycarbonate cages. No information was provided
about bedding materials. One experiment was conducted
to determine the optimum dose and age for observing
testosterone exposure effects. In a second experiment, 10
rats/group rats were castrated at 5 weeks of age and 7
days later gavaged with bisphenol A (99% purity) at
doses of 0 (ethanol/corn oil vehicle) 10, 100, or 1000 mg/
kg bw/day for 7 days. A second group of castrated 6week-old
males rats was gavaged with bisphenol A at 0,
50, 100, 250, or 500 mg/kg bw/day for 7 days. In a third
experiment, 10 castrated 6-week-old rats/group were
treated with 0.4 mg/kg bw/day testosterone by s.c.
injection in addition to gavaged bisphenol A at 50, 100,
250, or 500 mg/kg bw/day or flutamide at 1, 5, 10, or
25 mg/kg bw/day for 7 days. A positive control group
was given 0.4 mg/kg bw/day testosterone for 7 days.
[There is some confusion in the article regarding ages at
castration and start of treatment. For the first group of
bisphenol A-treated rats, it is reported that rats were
castrated at 5 weeks of age and treated at 6 weeks of
age. For the other groups of bisphenol A-treated rats,
the Methods section reported that treatment began at 6
weeks of age, but tables in the Results section
indicated that rats were castrated at 6 weeks of age.]
During the study, clinical signs were observed and body
weights were measured. Blood was collected and rats
were killed B24 hr after administration of the last
dose. Accessory reproductive organs were removed
and weighed. Serum luteinizing hormone (LH)
and testosterone concentrations were measured by
Birth Defects Research (Part B) 83:157–395, 2008