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

252 CHAPIN ET AL.
weights, bisphenol A intake was B1600 mg/kg bw/day
during the prebreeding stage and 1000 mg/kg bw/day
during gestation and at weaning.] The rats were mated
to males fed CE-2 basal pellet diet (Clea, Inc.), and GD 0
was defined as the day of the vaginal plug. Endpoints
associated with pregnancy, delivery, and nursing were
evaluated. Dam body weight and food intake were
measured. Offspring were not culled and were weaned
at 3 weeks of age. Dams were killed following weaning of
offspring. Serum levels of thyroid hormones were
measured in 2–4 dams/group. Implantation sites were
evaluated. Weights of several organs, including ovary,
were measured. The organs were fixed in 10% buffered
formalin and processed for histopathological evaluation.
Offspring (n 5 32–50/group) were evaluated for body
weight gain, preputial separation, and vaginal opening.
Beginning at 5 weeks of age and continuing for 12 weeks,
offspring in each group were subdivided into 2 groups
(n 5 17–21/group/sex) that received either undosed tap
water or tap water containing 2000 ppm N-nitrosobis (2hydroxypropyl)amine.
Offspring were killed at 25 weeks
of age. Serum thyroid hormone levels were measured.
Organs, including testis, ovary, and uterus were
weighed. In 5–19 offspring/sex/group, histopathological
examinations were conducted in organs targeted by Nnitrosobis
(2-hydroxypropyl)amine (lungs, thyroid, esophagus,
liver, and thymus). Data were analyzed by
Dunnett and w 2 tests. [Data for pre-and postnatal
survival were presented and apparently analyzed on a
litter basis. The offspring were apparently used as the
statistical unit in body weight analyses. It was not clear
if the dam or offspring were considered the statistical
unit in other analyses.]
Dam body weight was lower in the 1.0% bisphenol A
group fed MF diet compared to the MF diet control
during the gestation period and at weaning. Food intake
and maternal serum levels of triiodothyronine, thyroxine,
and thyroid-stimulating hormone were unaffected by
bisphenol A exposure. Changes in weights or histopathological
alterations of maternal organs, including
uterus and ovary, were not observed in the bisphenol A
groups. [Data were not shown by the study authors.]
Bisphenol A had no significant effect on mating, fertility,
duration of gestation, live-born pups, implantation loss,
or offspring viability through PND 21. In pups from
dams exposed to 1.0% bisphenol A fed MF diet
compared to pups from MF controls, body weights were
higher [by 11%] in females at 3 days of age and lower
in males and females at 10 days and 2 weeks of age [16–
22% decreases in males and 12–19% decreases in
females]. In pups from dams exposed to 1.0% bisphenol
A and fed soybean-free diet compared to pups from the
soybean-free controls, body weights of pups were
increased in males at 3 weeks of age [13% increase]
and in females at 10 days and 3 weeks of age [13–19%
increase]. Prenatal exposure to bisphenol A did not
affect preputial separation or vaginal opening. In 25week-old
rats that were not exposed to N-nitrosobis (2hydroxypropyl)amine,
prenatal bisphenol A exposure
was associated with some thyroid-stimulating hormone
elevations in males and females from the MF and
soybean-free diet groups. According to a statement in
the study abstract, the study authors did not consider the
effect on thyroid-stimulating hormone to be related to
bisphenol A exposure. There were no effects of N­
nitrosobis (2-hydroxypropyl)amine exposure on serum
thyroid-stimulating hormone, triiodothyronine, or thyroxin
levels or on thyroid histopathology. No effects were
observed on offspring organ weights. [With the exception
of uterus and ovary, no organ weight data were
shown.] Prenatal bisphenol A exposure was not associated
with significant differences in the development of
N-nitrosobis (2-hydroxypropyl)amine-induced neoplasms
in the offspring. The study authors concluded
that bisphenol A exposure did not induce tissue injury in
rat dams or their offspring or affect the development of
tumors in offspring exposed to N-nitrosobis (2hydroxypropyl)amine.
Strengths/Weaknesses: Weaknesses include highdoses
and inadequate sample sizes. This study appears
to discount the importance of certain effects on body
weight and thyroid-stimulating hormone levels that
might have received more attention in a study with a
non-tumor focus. Sample size is inadequate to address
neoplasm endpoints. Information is insufficient to judge
the appropriateness of the statistical analyses and hence
the reliability of findings.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process due
to small sample size, high-dose levels, and inappropriate
statistics.
Kobayashi et al. (2002), supported by the Japanese
Ministry of the Environment, examined the effect of
prenatal and lactational bisphenol A exposure on somatic
growth and anogenital distance in Sprague–Dawley rats.
The same rats were used to measure plasma hormone
levels and testicular testosterone content in a study by
Watanabe et al. (2003) and apparently thyroid function in
a study by Koybayashi et al. (2005). Rats were fed
standard laboratory feed (CE-2, CLEA Japan, Inc.). [No
information was provided about caging or bedding
materials.] Rats were randomly assigned to groups and 6
rats/group were gavaged with bisphenol A (99.8%
purity) at 0 (corn oil vehicle), 4, 40, or 400 mg/kg bw/
day from GD 6 through PND 20. GD 0 was defined as the
day a vaginal plug was observed, but the day of birth
was not defined. Doses were based on the study by
Kwon et al. (2000) [discussed in Section 3.2.3.3]. On
PND 7, litters were culled to 10 pups, with equal
numbers of males and females when possible. Offspring
were weaned on PND 21. Dams were weighed during
the study. Body weight and anogenital distance were
measured in offspring at 1, 3, and 9 weeks of age. Plasma
and testicular testosterone levels were measured at 9 and
36 weeks of age, and plasma LH and FSH concentration
were measured at 9 weeks of age Weights of liver, kidney,
and testis were examined in offspring at 3 and 9 weeks of
age. One to 10 (most often 6–10) offspring/group/sex
were examined for body weight and anogenital distance
at 1 week of age and 4–6/sex/group at 3 and 9 weeks of
age. A pair of male and female offspring/litter [assuming
authors meant 1/sex/litter] was examined for organ
weights, and 4–6 males/group were used in hormone
analyses at 3 and 9 weeks of age. Statistical analyses
included ANOVA followed by Dunnett test. [It was
not clear if the dam or litter was considered the
statistical unit.]
In the 40 mg/kg bw/day group, all pups from 1 dam
were found dead on PND 2. Four of 6 dams of the
400 mg/kg bw/day group died on GD 21, and all pups
Birth Defects Research (Part B) 83:157–395, 2008