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

308 CHAPIN ET AL.
average weight were injected s.c. on GD 30–90 with
5 mg/kg bw day bisphenol A (991% purity) dissolved in
cottonseed oil. Control pregnant ewes (n 5 16) were
administered vehicle injections. Lambs were born over
about a 1-month interval in early spring. Birth outcome
measurements included number and gender of offspring,
weight, height, chest circumference, genital
development, and measurement of blood insulin and
insulin-like growth factor-1. Lambs were cross-fostered
and group housed on PND 3. Lactating ewes were fed a
diet of corn and alfalfa hay. Lambs had free access to
standardized Shur Gain feed pellets. [The authors note
the presence of phytoestrogens in the feed but did not
provide quantification.] At weaning, female were
separated from male offspring, and the females were
housed in open air pens under natural photoperiod with
free access to feed pellets, as described above.
Maternal blood samples were taken on GD 50, 70, and
90 for measurement of bisphenol A using HPLC. The
number and sex of offspring in each treatment group,
weight, height, chest circumference, and genital development
were noted. Blood levels of insulin and insulinlike
growth factor 1 were assayed by RIA on PND 1. In
female offspring [n not indicated], blood was drawn
biweekly during the first 2 postnatal months for
determination of LH by RIA. Timing of puberty onset
was estimated through twice weekly blood draws for
progesterone (n 5 11/group). Estrus cycling patterns
were determined by frequent measurement of FSH, LH,
and progesterone by RIA in 3 female offspring/group
after synchronization with prostaglandin F2a at 40 weeks
of age. Statistical analyses were performed using
ANOVA, repeated measures ANOVA, or a linear mixed
model. A cluster algorithm was used to identify LH
pulses, with Student t-test to determine LH nadirs.
Blood levels of bisphenol A were significantly higher
in exposed pregnant ewes than controls at all sampling
times. The levels reached (37.473.3 mg/L) were compared
to exposure levels reported in pregnant women
[0.3–18.9 mg/L (Schönfelder et al., 2002b)]. No statistical
difference was reported in gestation length, number of
offspring, or sex. There were no significant differences in
female lambs in anogenital distance, insulin, or insulinlike
growth factor levels on PND 1. In female offspring,
prenatal bisphenol treatment significantly decreased
birth weight [by B11%], height [by B5%], and chest
circumferences [by B7%, all comparisons estimated
from a graph]. In male offspring exposed to bisphenol A,
there were no significant differences from control in birth
weight, height, chest circumference, or anogenital distance,
but anoscrotal:anonavel ratio was increased
significantly [by 21%]. Bisphenol A treatment increased
significantly levels of circulating LH [by B89%, estimated
from a graph] during the first 2 months of life in
female offspring. Onset of puberty was not affected by
treatment in bisphenol A-exposed female offspring, but
these females had a significantly longer first breeding
season [by B2 weeks] and larger number of cycles
during the first breeding season). Estrous cycle length
and progesterone levels were not different from controls.
The bisphenol A group had significantly lower peak and
total LH, and the amplitude of LH pulses was increased
significantly, whereas frequency showed no difference
from control group. No differences in FSH were seen
between groups. Progesterone secretion pattern showed
no difference between groups, despite perturbations in
LH patterns.
The authors concluded that prenatal exposure to
bisphenol A impairs growth in female fetuses and is
associated with dampening of the LH surge. Although
there was no apparent effect on progesterone production,
the authors suggested that the changes induced by
prenatal exposure of females could interfere with
fertility.
Strengths/Weaknesses: This study appears to have
been well-conducted with the utilization of multiple
endpoints in sheep. Weaknesses are the use of a single
dose level and the relatively small sample size. The
single time point for bisphenol A plasma determination
at an unknown time relative to s.c. injection is a
weakness.
Utility (Adequacy) for CERHR Evaluation Process:
This study is adequate though of limited utility.
3.2.10 Non-mammalian species. Although these
studies in non-mammalian species can be quite useful for
understanding mechanisms and environmental impacts,
the studies are not considered useful for the evaluation
process, because of the uncertain relationship between
human biology and that of the model species.
3.2.10.1 Invertebrates: Hill et al. (2002) supported by
the Council on Undergraduate Research and the Association
for Biological Laboratory Education, examined
the effects of bisphenol A on the development of 2
freshwater sponge species. (Heteromyenia sp. and Eunapius
fragilis). Sponge gemmules were incubated in
tissue culture wells containing bisphenol A [purity not
indicated] at 0, 0.16, 16, 80, or 160 ppm [mg/L]. The
control group was incubated in the spring water vehicle.
There were 5 replicates/treatment. Nonylphenol and
ethylbenzene were also examined. Growth was measured
on Days 3, 6, and 9. Because growth patterns were
similar at all 3 evaluation periods, statistical analyses
were conducted only for Day 6 data. Data were analyzed
by ANOVA and Tukey multiple comparison test. In both
species, abnormal development or malformation of the
water vascular system was observed at a bisphenol A
dose of 16 ppm and germination was completely inhibited
at 80 and 160 ppm. Significantly reduced growth
rates were observed in Heteromyenia sp. at 160 ppm.
Similar effects were observed with nonylphenol and
ethylbenzene. The study authors stated that sponges may
prove useful for examining endocrine-disrupting
compounds.
Strengths/Weaknesses: This study used a unique
model with a focus on the aquatic system.
Utility (Adequacy) for CERHR Evaluation Process:
This study may have utility for environmental assessment,
but is not useful for human risk assessment.
Roepke et al. (2005), supported by the National
Oceanic and Atmospheric Administration, examined
the effects of bisphenol A exposure on development of
two species of sea urchin, Strongylocentrotus purpuratus
and Lytechinus anamesus. In dose–response studies, sea
urchin embryos were incubated from 1–96 hr postfertilization
in media containing bisphenol A [purity
not indicated] at 0, 250, 500, 750, or 1000 mg/L [culture
ware not discussed]. Development toxicity was assessed
at 96 hr by examining larvae at the pluteus stage. The
larvae were categorized as normal, delayed, abnormal,
elongated, or hatched. Data were obtained in 3 replicates.
Birth Defects Research (Part B) 83:157–395, 2008