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

group, as well as 19 offspring from 11 dams in the
0.2 mg/kg/d 17a-ethinyl estradiol group (G. Schönfelder,
personal communication, July 20, 2007)]. [Exact
litter representation for animals collected during
diestrus was not provided.]Vaginas were fixed in Bouin
solution and a histopathological evaluation was conducted.
Western blot analyses were conducted to
measure expression of ERa and ERb. [It does not appear
that statistical evaluations were conducted.]
Qualitative descriptions of vaginal histopathology
changes and ER expression were provided by the study
authors. Low-dose animals killed during the estrous
stage lacked keratinization of the surface epithelium and
demonstrated reduced thickness of the total epithelium.
Similar but less pronounced effects were observed in rats
of the high-dose bisphenol A group. Vaginal findings
were similar in the positive control group, and slight
desquamation of the superficial layers was also observed.
There were no differences in vaginal histopathology
findings in rats killed during the diestrous stage. No
ERb was observed in vaginas of rats from any treatment
group. Full-length ERa expression was not observed in
either bisphenol A group during estrus, but ERa in the
bisphenol A-exposed groups did not differ from the
control group during the diestrous stage. ERa in vaginas
obtained from the positive control group was either
reduced or was not detected. The study authors
concluded that altered vaginal morphology following
bisphenol A treatment appears to be due to downregulation
of ERa.
Strengths/Weaknesses: Vaginal histopathology of female
offspring is of interest but the quality of the study
cannot be judged due to unclear methodology. Uncertainty
about the numbers of animals, the number of
offspring examined and the lack of statistical accounting
for litter effects are significant weaknesses.
Utility (Adequacy) of the CERHR Evaluation Process:
This study is inadequate for the evaluation process for
the reasons detailed above.
Schönfelder et al. (2004), supported by the German
Federal Ministry for Environmental Protection and
Radiation Security, examined the effects of prenatal
bisphenol A exposure on the rat uterus. [No information
was provided about composition of feed, caging, or
bedding.] Sprague–Dawley rats [number treated not
specified] were gavaged with bisphenol A [purity not
reported] at 0 (2% corn starch vehicle), 0.1, or 50 mg/kg
bw/day on GD 6–21. [Author clarified that the purity of
Table 72
Uterine Effects in Rats Exposed to Bisphenol A During
Prenatal Development
Dose, mg/kg bw/day
Endpoint 0.1 50
Thickness of luminal epithelium
Epithelial nuclei a
Epithelial nuclei with
condensed chromatin
Epithelial cells with cavities
ERa positive cells in epithelium
ERb-positive cells in uterine tissue
2
m69%
m2.7-fold
m2.1-fold
2
k88%
k38%
m89%
m3.1-fold
m 1.9-fold
m67%
k88%
a It is unclear if authors were referring to numbers of nuclei.
Birth Defects Research (Part B) 83:157–395, 2008
BISPHENOL A
241
bisphenol A was Z98%; Altromin 1324 rodent chow
was used (obtained from Altromin GmbH); bedding
was wood shavings obtained from Altromin GmbH;
caging was Type III macrolon cages (G. Schönfelder,
personal communication, July 20, 2007).] The high
bisphenol A dose was selected because it was reported
to be the no observed effect level (NOEL) recommended
by the Society of the Plastics Industry. A positive control
group was gavaged with 0.2 mg/kg bw/day ethinyl
estradiol on GD 6–21. Estrous cyclicity was examined for
3 weeks in 6 female offspring/group beginning at 3
months of age. Six female offspring/group were killed at
4 months of age on the day of estrus. Body and
reproductive organ weights were measured. Uteri were
fixed in methacarn solution and sectioned. Examinations
of uterine morphology were conducted. Immunohistochemistry
techniques were used to detect ERa and ERb
in the uterus, and results were verified by Western blot.
Data were analyzed by Mann–Whitney test. [It was not
clear if data were analyzed on a per litter or per
offspring basis.] [Author states that each female came
from a different litter so the data were analyzed on a
per litter basis (G. Schönfelder, personal communication,
July 20, 2007).] Statistically significant findings are
summarized in Table 72. Effects observed at both dose
levels were increased epithelial cell nuclei, epithelial
nuclei with condensed chromatin, and epithelial cells
with cavities and reduced ERb-positive cells in uterine
tissue. Additional effects observed only at the high-dose
included decreased thickness of luminal epithelium and
increased ERa-positive cells in the epithelium. Similar
findings were observed following treatment with ethinyl
estradiol. The study authors concluded that prenatal
bisphenol A exposure causes uterine effects in rat
offspring.
Strengths/Weaknesses: A strength is the examination
of effects on uterine indices in female offspring. A slight
weakness is the use of only 6 females per group;
however, the panel noted that the results appeared to
be consistent across animals and across endpoints,
especially in the 50 mg/kg bw/day treatment group.
Utility (Adequacy) for CERHR Evaluation Process:
This study is adequate and of high utility for the
evaluation process.
Wistuba et al. (2003), supported by the German
Federal Ministry of Education and Science, examined
the effects of prenatal exposure on testicular histology
and sperm endpoints in rats. [No information was
provided about chow, bedding, or caging.] Sprague–
Dawley rats were gavaged with 0 (2% corn starch
suspension vehicle), 0.1, or 50 mg/kg bw/day bisphenol
A [purity not reported] on GD 6–21 (GD 0 5 day of
sperm detection). A third group was treated with
0.02 mg/kg bw/day ethinyl estradiol. The high-dose
was said to correspond to the current accepted no
observed adverse effect level (NOAEL) and the lower
dose was selected to determine if effects occurred at
lower doses. It appears that the number of dams treated
was 2 in the control group, 4 in the low-dose group, 1 in
the high-dose group, and 4 in the ethinyl estradiol group.
Litters were weighed during the lactation period. Pups
were weaned on PND 22 [day of birth not defined].
Male offspring were killed between the ages of B9–12
months. The number of males killed was 5 from 2 litters
in the control group, 15 from 4 litters in the low-dose