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

BISPHENOL A
Table 73
Effects of Pubertal Exposure to Bisphenol A on ERa Levels in Sexually Dimorphic Hypothalamic Regions in the Rat a
To oil control
Comparison, % change
Bisphenol A Ethinyl estradiol Males to females
Region PND Males Females Males Females Control Bisphenol A Ethinyl estradiol
Arcuate nucleus
Ventromedial nucleus
Medial preoptic area
37
90
37
90
37
90
2
2
2
2
2
2
2
2
[m50]
2
2
2
2
2
[m112]
2
2
2
2
2
2
2
2
[m85]
2
2
2
2
2
2
2
2
2
2
2
[m50 in females]
a Ceccarelli et al. (2007).
Comparisons estimated from a graph.
m,k,2 Statistically significant increase, decrease, or no change compared to vehicle-treated, orchiectomized control.
maintained under a reversed light cycle. On PND 23–30,
rats (n 5 14/group) were given bisphenol A 40 mg/kg
bw/day, ethinyl estradiol 0.4 mg/kg bw/day, or peanut
oil vehicle. Half the offspring (n 5 7/group) were killed
on PND 37 and half on PND 90. Females killed on PND
90 were killed in estrus. Blood samples were taken and
animals were formalin perfused. Brains were harvested,
post-fixed, and cryopreserved. Immuno-histochemistry
was performed on frozen sections for comparative ERa
level analysis, with a focus on sexually dimorphic
regions of the hypothalamus: the arcuate nucleus,
ventromedial nucleus, and medial preoptic area. Two
or three sections/rat were stained, equivalent field areas
outlined, and ERa-positively stained nuclei counted
under light microscopy by an evaluator blinded to all
experimental parameters. Serum testosterone and 17bestradiol
were determined by RIA. Statistical analyses
were performed using ANOVA and post-hoc least
significant difference test.
The results for ERa are shown in Table 73. There were
few statistically significant difference between controls
and treated rats. Effects identified for ethinyl estradiol
were not seen with bisphenol A with the exception of an
increase in bisphenol A-treated females compared to
males in ERa at 90 days in the medial preoptic area. On
PND 37, testosterone was significantly reduced [B40%]
in bisphenol A treated males compared to control males.
There were no significant effects of bisphenol A
treatment on 17b-estradiol or on testosterone/17b-estradiol
ratio.
The authors conclude that exposures to bisphenol A at
40 mg/kg bw/day during early puberty can induce both
short-term and long-term changes in sexually dimorphic
regions of the brain and circulating testosterone/17bestradiol
ratio.
Strengths/Weaknesses: This interesting and novel
manuscript examined the potential for the ethinyl
estradiol positive control and bisphenol A administered
before puberty, but after the most sensitive period (i.e.,
PND 3–10), to modulate ER and steroid hormones during
puberty and sexual maturity. It appears that the authors
tried to remove the potential for bias by blinded
quantification of ER-positive neurons. The oral route of
exposure was relevant. These data must be linked
Birth Defects Research (Part B) 83:157–395, 2008
267
2
2
[m70 in males]
2
2
[m118 in females]
functionally to the results of Della-Seta et al. (2006). A
weakness is that hormonal measurements were taken at
single time points.
Utility (Adequacy) for CERHR Evaluation Process:
These data are adequate and of high utility for the
evaluation process.
3.2.4 Rat—parenteral exposure postnatally.
3.2.4.1 Reproductive endpoints: Fisher et al. (1999),
supported by the European Centre for Ecotoxicology of
Chemicals and Zeneca, examined the effect of neonatal
bisphenol A exposure on excurrent ducts of the rat testis.
On PND 2–12 (PND 1 5 day of birth), Wistar rat pups were
s.c. injected with the corn oil vehicle or 37 mg/kg bw/day
bisphenol A [purity not given]. The dose wasbased on the
solubility limit in oil. [The number of rats treated was not
indicated nor was relationship to litter, but based on the
number of rats examined in each time period (B3–7 in
treated group and 5–20 in control group), it appears that
there were B25/group in the bisphenol A group and B48
in the vehicle control group. No information was
provided about caging or bedding materials.] Seven other
compounds were also examined but will not be discussed,
with the exception of a brief explanation of results obtained
with 0.0037–0.37 mg/kg bw/day diethylstilbestrol. Rats
were killed at 10, 18, 25, 35, and 75 days of age. Testes
and epididymides were removed and fixed in Bouin
solution. Immunohistochemistry techniques were used to
examine water channel aquaporin-1 levels. Morphology of
rete testis and efferent duct were examined. Data were
analyzed by ANOVA.
In the bisphenol A group, the only effect on testis
weight was a significant decrease [B40%] at 35 days of
age. Epithelial cell height in the efferent ducts was
significantly reduced [by B15%] at 18 and 25 days of
age, but not at later time periods. There was no effect on
expression of water channel aquaporin-1 protein or
morphology of the rete testis. Treatment with most
diethylstilbestrol doses resulted in reduced testicular
weights at all ages, decreased expression of water
channel aquaporin-1 protein, and decreased epithelial
cell height in efferent ducts at 25 days of age and
younger, and fluid retention and enlargement of rete
testis, which was most severe at PND 18 and 25. The
study authors concluded that the magnitude and