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

242 CHAPIN ET AL.
group, 5 from 1 litter in the high-dose group, and 10 from
4litters in the ethinyl estradiol group. Testes were fixed in
Bouin solution, and Sertoli cells were counted. Spermatogenesis
was evaluated by examining germinal epithelia
for cell death and distribution of various cell populations.
Data were analyzed by ANOVA. [It appears that at
least some data were analyzed on a per litter basis. In
addition, analyses were done to determine intralitter
variability and thus the numbers of animals per group
that needed to be analyzed.]
Examination of tubule cross sections revealed qualitatively
normal spermatogenesis in the bisphenol A
groups. A comparison of Sertoli cell numbers in
littermates revealed high variability (20–27%) in the
0.1 mg/kg bw/day group. A comparison of Sertoli cell
numbers in the 4 litters from the 0.1 mg/kg bw/day
group revealed almost identical results between litters.
Sertoli cell numbers/organ were significantly increased
by 19.4% in the low-dose group and 19% in the high-dose
group. Bisphenol A had no significant effect on Sertoli
cell numbers/g testis weight. The opposite situation
occurred in the ethinyl estradiol group, with no
significant effects on Sertoli cell numbers/organ but a
significant increase in Sertoli cell numbers/g testis
weight. Testis weight was not affected by bisphenol A
treatment but was decreased in the ethinyl estradiol
group. The study authors concluded that the study does
not support the hypothesis of disruption of the male
reproductive system by bisphenol A exposure.
Strengths/Weaknesses: The conceptual strength is the
focus on the male reproductive tract/function. However,
a weakness is that there were too few animals to provide
reliable data.
Utility (adequacy) for the CERHR Evaluation Process:
This study is inadequate based on insufficient
sample size (n 5 2–4).
Thuillier et al. (2003), supported by National Institute
of Environmental Health Sciences (NIEHS), examined a
possible role for the platelet-derived growth factor
system in estrogenic effects induced by bisphenol A in
rats exposed during gestation. The effects of other
compounds such as genistein and coumestrol were also
examined but will not be discussed here. Pregnant
Sprague–Dawley rats were gavaged with bisphenol A
at 0 (corn oil vehicle) or 0.1, 1, 10, or 200 mg/kg bw/day
from GD 14 through birth (PND 0). Additional rats were
s.c. injected with diethylstilbestrol at 0.01–2 mg/kg bw/
day during the same period. [No information was
provided about number of rats treated, purity of
bisphenol A, feed, or materials used in bedding and
caging.] Male offspring were killed on GD 21 or PND 3
and testes were collected. Expression of mRNA or
protein for platelet-derived growth factor receptor-a
and platelet-derived growth factor receptor-b were
determined in testes using RT-PCR, in situ hybridization,
or immunohistochemistry. Statistical analyses included
unpaired t-test with Welch correction. [It was not clear if
the litter or offspring were considered the statistical
unit.]
Expression of mRNA for platelet-derived growth
factor receptor-a and -b was significantly increased at
bisphenol A doses Z1 mg/kg bw/day in testes from 3day-old
rats. All other experiments with bisphenol A
were conducted with a single dose of 200 mg/kg bw/
day. In situ hybridization examination of testes from 3­
day-old rats from the bisphenol A group revealed an
increase in expression of platelet-derived growth factor
receptor-a mRNA in testicular interstitium and plateletderived
growth factor receptor-b mRNA in interstitium
and seminiferous cords. Exposure to bisphenol A
resulted in slightly increased platelet-derived growth
factor receptor-a protein expression and strong expression
of platelet-derived growth factor receptor-b in
gonocytes from 3-day old rat testes. Immunolocalization
studies in testes from 21-day-old fetuses revealed that
exposure to 200 mg/kg bw/day bisphenol A did not
affect expression of platelet-derived growth factor
receptor-a protein in gonocytes, but platelet-derived
growth factor receptor-b protein appeared to be increased
in gonocytes and Sertoli cells. Diethylstilbestrol
tended to have a biphasic effect with increased expression
of platelet-derived growth factor receptor-a and -b
mRNA in 3-day-old rat testis at low doses and decreased
expression at the high-dose. Treatment with 1 mg/kg bw/
day diethylstilbestrol decreased mRNA expression of
platelet-derived growth factor receptor-a in interstitium
and increased platelet-derived growth factor receptor-b
mRNA expression in seminiferous cords. Immunoreactivity
for platelet-derived growth factor receptor-a
protein was maintained but there was a minimal level
of platelet-derived growth factor receptor-b protein
expression in 3-day-old rat testes following exposure to
1 mg/kg bw/day diethylstilbestrol. In testes obtained
from 21-day-old fetuses, expression of platelet-derived
growth factor receptor-a protein was decreased in Sertoli
and interstitial cells and expression of platelet-derived
growth factor receptor-b protein was apparently increased
following exposure to diethylstilbestrol. The
study authors concluded that the platelet-derived growth
factor receptor pathway may be a target for estrogens in
the testis, but the findings do not exclude the possibility
that effects may have occurred through an ER-independent
mechanism.
Strengths/Weaknesses: Endpoints are a strength, but
inadequate methodological detail (i.e., sample size or
adequate control for litter effects) precludes any informed
judgment of study quality.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process based
on insufficient methodological details.
Wang et al. (2004), supported by NIEHS, examined the
effects of prenatal bisphenol A exposure on expression of
ER-associated proteins in rat testis. The effects of
genistein and coumestrol were also examined but will
not be discussed here. Pregnant Sprague–Dawley
rats [apparently 3/group] were gavaged with corn oil
vehicle or bisphenol A at 0.1–200 mg/kg bw/day from
GD 14 (14 days post-coitum) through birth. Additional
rats were s.c. injected with 0.01–2 mg/kg bw/day
diethylstilbestrol during the same time period. [No
information was provided about feed, caging
and bedding material, or compound purity.] Male
offspring from three independent litters were killed on
GD 21, PND 3, or PND 21. Western blot, RT-PCR, and
immunohistochemistry techniques were used to measure
expression of protein or mRNA for Hsp90, Hsp90a, p23,
CYP40, Hsp70, and/or ERb. Spermatogonia were
quantified in PND 21 rat testis. Data were analyzed
by unpaired t-test. The dam was considered the
statistical unit.
Birth Defects Research (Part B) 83:157–395, 2008