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

298 CHAPIN ET AL.
PND 21 and housed individually in polycarbonate cages.
At 12 weeks of age, males were weighed and 25 males/
group were killed and necropsied. During necropsy of
males that had been exposed during prenatal development
or during adolescence, testes, epididymis, and
seminal vesicles with coagulating glands were weighed.
In the study conducted in adult mice, it was noted that
ventral prostates were not weighed due to difficulties in
obtaining only prostate and determining the precise
weight of the organ. Epididymal sperm counts were
obtained. Histopathological examinations were conducted
for reproductive organs fixed in Bouin solution.
For males exposed during gestation, the litter was
considered a single sample. Data were analyzed by
Bartlett’s test to determine homogeneity of variance,
followed by ANOVA when homogeneity of variance was
obtained or Wallace–Wallace analysis of ranks when
variance was not homogenous. Dunnett test was used for
multiple comparisons.
There were no significant effects on embryo mortality
after birth, body weight gain, or terminal body weight.
[Data were not shown.] The only reproductive organ
weight effect was a significant, but non-dose-related [6%]
decrease in absolute seminal vesicle weight in the lowdose
bisphenol A group. Organ weights were not affected
in males exposed during adolescence. Sperm density was
unaffected by bisphenol A exposure. No treatment-related
lesions were observed in testes or other reproductive
organs including ventral prostate. [Data were not shown.]
The study authors concluded that low-dose bisphenol A
exposure of mice did not reduce sperm density or disrupt
male reproductive system development.
Strengths/Weaknesses: Strengths are the use of three
low dose levels, the oral route of administration, the
careful description of methods, the use of a lowphytoestrogen
diet, and the confirmation that the strain
of mice used was estrogen sensitive.
Utility (Adequacy) for CERHR Evaluation Process:
This study is adequate and of high utility for the
evaluation process.
Kabuto et al. (2004), supported by the Kagawa
Prefectural College of Health Sciences, examined the
role of oxidative stress in bisphenol A-induced toxicity in
mice. ICR mice were fed standard laboratory chow
containing 24% protein (MF; Oriental Yeast Co.). [No
information was provided about bedding or caging
materials.] From 1 week before mating through gestation
and lactation, 6 mice/group were given drinking water
containing the 1% ethanol vehicle or bisphenol A [purity
not reported] at 5 or 10 mg/L. [Based on the reported
water intake of 5 mL/day and an assumed body weight
of 0.02 kg (USEPA, 1988), it is estimated that bisphenol
A intake in mice at the start of pregnancy was 0.0013 or
0.0025 mg/kg bw/day.] Mice gave birth about 3 weeks
following mating and pups were housed with dams for 4
weeks. [Based on an assumed body weight of 0.0085 kg
and assumed water intake rate of 0.003 L/day (USEPA,
1988), it is estimated that intake of bisphenol A in
weanling males was 0.0018 or 0.0035 mg/kg bw/day]. At
4 weeks of age, male pups were killed and brain, kidney,
liver, and testis were weighed in 8–13 mice/group.
Tissues were homogenized to determine activities of
superoxide dismutase, catalase, and glutathione peroxidase
and concentrations of glutathione and L-ascorbic
acid in 6–8 mice/group. Tissue level of thiobarbituric
acid-reactive substance, a biogenic macromolecular
peroxidation indicator, was measured in 6 mice/group.
Data were analyzed by ANOVA followed by Scheffe F
test. [It appears that offspring were considered the
statistical unit in some analyses.]
Organ weight effects included decreased brain weight
at the low dose, decreased kidney weight at the highdose,
and decreased testis weight at both doses. [Relative
organ weights were not determined.] In the high-dose
group, thiobarbituric acid-reactive substance levels were
increased in brain, kidney, and testis. Changes in
antioxidant enzyme levels included decreased catalase
activity in testis and increased glutathione oxidase
activity in kidney. No significant effects were observed
for superoxide dismutase activity or glutathione or
ascorbic acid levels in any of the tissues examined. The
study authors concluded that bisphenol A exposure
during gestation and lactation results in oxidative stress
and peroxidation in offspring that ultimately lead to
underdevelopment of brain, kidney, and testis.
Strengths/Weaknesses: The delivery of bisphenol A in
drinking water at low dose levels is a strength. Weaknesses
include small sample size of exposed dams
(n 5 6), inappropriate use of the pup as the experimental
unit in statistics, and mechanistic data without functional
correlates.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process due
to inappropriate statistical procedures and small sample
size.
Takao et al. (2003), support not indicated, examined
the effects of bisphenol A exposure on expression of ERa
and ERb in the testis of young mice. [No information
was provided about feed, caging, or bedding materials.]
Three-week-old male C57BL/6 mice (n 5 7/group) were
administered bisphenol A [purity not indicated] through
drinking water at 0 (ethanol vehicle), 0.5, or 50 mg/L for
8 weeks. [Assuming a weanling mouse drinks B0.35 L/
kg bw/day (USEPA, 1988), bisphenol A intake would
have been B0, 0.175, or 17.5 mg/kg bw/day.] The
stability of bisphenol A was not determined, but water
bottles were changed two times a week to maintain a
stable concentration of bisphenol A in drinking water.
Mice were killed at an unspecified period following
exposure, and the testis and spleen were weighed. The
testis was examined for ERa- and ERb-positive cells
using an immunohistochemistry method and ERa and
ERb mRNA using a semi-quantitative RT-PCR technique.
Data were analyzed by ANOVA followed by Fisher
protected least significant difference test.
Exposure to 50 mg/L bisphenol A resulted in a
decreased number of ERb-positive cells and increased
number of ERa-positive cells. Expression of ERb mRNA
was decreased and expression of ERa mRNA was
increased following exposure to 50 mg/L bisphenol A.
There were no differences in body weight or absolute or
relative weights of testis or spleen following bisphenol A
treatment. The study authors concluded that differential
modulation of ERa and ERb could be involved in effects
observed following bisphenol A exposure.
Strengths/Weaknesses: The delivery of bisphenol A in
drinking water and the measurement of ER in the testis
are strengths. The lack of clarity on age at sacrifice,
limited number of endpoints assessed, and marginal
sample size (n 5 7) are significant weaknesses.
Birth Defects Research (Part B) 83:157–395, 2008