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

Experiment
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BISPHENOL A 343
Table 89
Conditions Used in Experiments to Study Bisphenol A Effects on Sperm Production in Rats a
Bisphenol A doses
mg/kg bw/day No. rats/group Diet/water Caging
0, 0.020, 2, or 200
0, 0.020, 2, or 200
0, 0.020, 2, or 200
0, 0.020, 2, or 200
0
a Ashby et al. (2003).
10
10
10/bisphenol A
group 20/control group
10/bisphenol A
group 20/control group
10
To obtain more dose–response information, Sakaue
et al. (2001) repeated the study in 8 rats/group dosed
[assumed by gavage as in the first study] with 0.000002,
0.00002, 0.0002, 0.002, 0.020, 0.200, or 2 mg/kg bw/day
bisphenol A. [It is assumed that ages of rats, treatment
period, and observation periods were the same as in the
first study.] Body and testis weights were not affected by
bisphenol A treatment at Week 18. At Week 18,
significant decreases in daily sperm production and
daily sperm production/g tissue were observed at 0.020,
0.200, and 2 mg/kg bw/day. [The decrease compared to
control was estimated from a graph. For daily sperm
production, the decreases were B30% at 0.020 mg/kg
bw/day, B34% at 0.200 mg/kg bw/day, and B32% at
2 mg/kg bw/day. For daily sperm production/g tissue,
the decreases were B24% at 0.020 mg/kg bw/day, B32%
at 0.200 mg/kg bw/day, and B28% at 2 mg/kg bw/day.]
In a third experiment, rats were given a single oral
dose of 0.020 mg/kg bw bisphenol A. Six hours later, the
rats were killed, the right testis was homogenized, and
the cytosol was examined for protein expression using
two-dimensional polyacrylamide gel electrophoresis.
Changes in intensity and mobility were noted for 3
unidentified proteins. The study authors concluded that
the dose–response curve for bisphenol A affects on
spermatogenesis in the adult rat was monotonic rather
than having an inverted U-shape.
Strengths/Weaknesses: This study used a relevant
route of administration and multiple doses. A weakness
is the brief exposure period. Variability in control daily
sperm production between the first and second study is
disturbing; given the small sample (5 or 8/group), this
variability severely decreases confidence in the data. No
histopathologic correlate was presented.
Utility (Adequacy) for CERHR Evaluation Process:
This study is adequate but of limited utility due to small
sample and variable control values between experiments.
Ashby et al. (2003), support not indicated, examined
the effects of bisphenol A exposure on sperm production
in rats. The study attempted to replicate earlier findings
from Sakaue et al. (2001). Five independent experiments
were conducted, and the conditions for each experiment
are summarized in Table 89. Some of the experiments
used the same conditions as the Sakaue et al. (2001)
study, including stainless steel cages with no bedding,
CE2 diet (CLEA, Tokyo, Japan), and glass water bottles.
In the first 4 studies, 10–20 adult (B13-week-old)
Sprague–Dawley rats/group were gavaged with bisphenol
A (99% purity) at 0 (ethanol/corn oil vehicle), 0.020,
Birth Defects Research (Part B) 83:157–395, 2008
RM3/Automatic system
5002/Glass bottles
5002/ Glass bottles
CE2/ Glass bottles
RM3, 5002, or CE2/not
specified
Stainless steel, unspecified bedding
Stainless steel, no bedding
Stainless steel, no bedding
Stainless steel, no bedding
Not specified
2, or 200 mg/kg bw/day for 6 days. Concentrations of
dosing solutions were verified. In the fifth study, rats fed
different diets were gavaged with vehicle for 6 days. Rats
were fed 1 of 3 diets as indicated in Table 89. Phytoestrogen
aglycone content of the feed was measured.
Respective concentrations of daidzein, genistein, and
coumestrol in each feed were reported at 94, 62, and
0.6 mg/g diet for Rat and Mouse No. 3 (RM3; Special Diet
Services Ltd.); 40, 23, and 0.1 mg/g diet for 5002 (Purina
Mills); and 157, 106, and 2.2 mg/g CE2 diet. Ten rats were
used in each group, except in third and fourth studies,
where 20 control rats were split into 2 groups before
dosing. Rats were administered drinking water through
an automatic system in the first study and via glass
bottles in the other studies. In the first study, rats were
housed 3/cage at the start of the study and 2/cage later
in the study. In the other 4 studies, rats were housed 2/
cage. Rats were weighed during the study. Animals were
killed at 18 weeks of age, 5 weeks after the start of
dosing. Liver, kidney, and reproductive organs were
weighed, and sperm counts were obtained. In the first 4
studies, data were analyzed by ANOVA, ANCOVA for
organ and body weights, and Dunnett test. Results from
all 4 studies were also analyzed by ANOVA in an attempt
to increase study power. Data from the fifth study were
analyzed by Fisher least significant difference test.
In the 4 studies that compared the effects of bisphenol
A exposure to a vehicle control group, there were no
significant effects of bisphenol A exposure on sperm
count, daily sperm production, or weights of body, liver,
kidney, testis, prostate, epididymis, or seminal vesicle.
One animal exposed to 200 mg/kg bw/day bisphenol A
in the third study was reported to have unexpectedly
small testes and epididymides, but the study authors
indicated that inclusion of this animal in later statistical
analyses had no effect on outcome. One animal in the
200 mg/kg bw/day group in the fourth study had a
small testis. No significant effects were observed when
data from the first 4 experiments were pooled and
analyzed. The study authors noted that some endpoints
were variable from one experiment to the other. It was
noted that prostate weights were 10% lower in animals
from Experiment 1 than from Experiments 2–4. Sperm
counts and daily sperm production were reportedly
different in control animals from Experiment 1 compared
to Experiment 2. It was noted that rats were fed different
diets in Experiment 1 (RM3) and Experiment 2 (5002),
and a study to examine the effects of feed was
conducted. In the study examining effects in rats fed