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

glands were also conducted. Data were analyzed by
ANOVA, least significant difference test, and t-test. [The
statistical analyses considered litter differences, method
unstated.]
At 1 month of age, the rate of ductal migration into the
stroma was increased in the low-dose group and
decreased in the high-dose group; values in the 2
treatment groups were significantly different from one
another but neither dose group was significantly
different from the control group. Bisphenol A treatment
increased percentages of ducts and buds at 6 months of
age. Bromodeoxyuridine incorporation was decreased in
epithelial cells at both doses at 10 days of age, decreased
in stromal cells at the high-dose at 1 month of age, and
increased in stromal cells at both dose levels at 6 months
of age. At 1 month of age, the ratio of bromodeoxyuridine-positive
epithelial to stromal cells was 4:1 in the
control group, 2:1 in the 0.000025 mg/kg bw/day group,
and 6:1 in the 0.000250 mg/kg/bw/day group. The
percentage of alveoli containing secretory products was
increased at the low dose at 6 months of age. The study
authors concluded gestational exposure to low doses of
bisphenol A alters timing of DNA synthesis in mammary
epithelium and stroma, resulting in a histoarchitecture
that is not typical for a virgin mouse.
Strengths/Weaknesses: The examination of the mammary
gland, a system not often studied, is a strength. A
critical weakness is the uncertainty of the DMSO
concentration as a vehicle and therefore pump performance.
An additional weakness is that the proliferative
changes reported in mammary tissues in virgin mice
have not been satisfactorily established as precursors of
breast cancer.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process given
exposure uncertainties.
Markey et al. (2003), supported by NIH and the
Massachusetts Department of Public Health, examined
the effects of prenatal bisphenol A exposure on development
of the female reproductive system and mammary
gland in mice. CD-1 mice were fed Purina Rodent
Chow that tested as having negligible estrogenicity.
Cages and bedding tested negative for estrogenicity in
the E-SCREEN assay. Water was provided in glass
bottles. Mice (n 5 6–10/group) were administered bisphenol
A [purity not indicated in the manuscript;
9772% per A. Soto, personal communication, March 2,
2007] at 0 (DMSO vehicle), 0.000025, or 0.000250 mg/kg
bw/day by s.c. pump from GD 9 through the remainder
of pregnancy (GD 1 5 day of vaginal plug). [The dose
levels were incorrect in the original and were corrected
by an erratum (Markey et al., 2004).] Number of
offspring, sex ratio, body weight, and age at vaginal
opening were assessed. Beginning at 3 months of age and
continuing for 2 weeks, estrous cyclicity was assessed by
visual examination of the external vagina and confirmation
by vaginal smears. Female offspring (6–10/group)
were killed at 1, 3, 4, 6, 9, and 12 months of age on the
afternoon of proestrus. Reproductive organs were
grossly assessed, and morphometric measurements were
obtained for ovary and mammary gland. [Although
the methods section suggests that morphometric measurements
were obtained at each time period of
sacrifice, it does not appear that the measurements
were taken at 12 months of age. The 1-month data
Birth Defects Research (Part B) 83:157–395, 2008
BISPHENOL A
291
were reported in a previous publication (Markey
et al., 2001a).] A histopathological evaluation of the
ovary was conducted at 3 months of age. Reproductive
organ weights were obtained at 1, 3, and 6 months
of age. [As in other studies reported from this
laboratory, different litters were represented at each
time period (A. Soto, personal communication
March 2, 2007).] Statistical analyses included ANOVA,
Kruskal–Wallis, and Mann–Whitney tests. [It was not
clear if the litter or offspring was considered the
statistical unit.]
Bisphenol A exposure had no significant effect on litter
size or sex ratio. A significant interaction between age for
body weight and treatment was reported from 2–12
months of age but the effect on body weight was not
explained. No significant effects were observed for
vaginal opening in treated mice. Significant increases
were observed in percentages of 3-month-old mice with
estrus/metestrus for Z4 or 8 days. At 6 months of age,
the incidence of fluid-filled ovarian bursae was increased
in both treatment groups. Reproductive organ weights
were not affected at 1 or 6 months of age, but at 3 months
of age, absolute and relative (to body weight) weights of
vagina were decreased in the high-dose group. The
percentage of ovary tissue consisting of antral follicles
was increased in the high-dose group at 3 months of age.
No significant differences were observed for mammary
structures at 4 months of age. At 6 months of age, the
percentage of alveolar buds/lobulo-alveoli was increased
in both dose groups compared to the control group. The
percentage of alveolar buds/lobulo-alveoli was decreased
in the low-dose group compared to control
group at 9 months of age. The study authors concluded
that exposure of mice to environmentally relevant doses
of bisphenol A during the development of estrogensensitive
tissues results in effects that are manifested in
adulthood.
Strengths/Weaknesses: The examination of the mammary
gland, a system not often studied, is a strength. A
critical weakness is the uncertainty of the DMSO
concentration as a vehicle and therefore pump
performance.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process given
exposure uncertainties.
Vandenberg et al. (2007), supported by NIEHS and
Tufts, examined the effects of prenatal bisphenol A
exposure on mouse mammary gland development. CD-1
mice were fed Harlan Teklad 2008, which was reported to
contain 20 fmol/g estrogen equivalents. The type of
caging and bedding used was not reported but they were
stated to test negative for estrogenicity in the E-SCREEN.
Water was supplied in glass bottles. On GD 8 (GD
1 5 day of vaginal plug) mice were implanted [subcutaneous
(A. Soto, personal communication, March 2,
2007)] with osmotic pumps that delivered the 50% DMSO
vehicle or bisphenol A [purity not reported in manuscript;
9772% per A. Soto, personal communication,
March 2, 2007] at 0.000250 mg kg bw/day. The bisphenol
A dose was selected because it was predicted (or
estimated) to be environmentally relevant and shown
to alter mammary endpoints (Markey et al., 2001a;
Muñoz-de-Toro et al., 2005). Pumps were left in place
until dams were killed on GD 18. [The number of dams
treated was not reported in the paper. The Expert Panel