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

316 CHAPIN ET AL.
of testes and combs of male chickens. Beginning at 2
weeks of age, male white Leghorn chicks were orally
dosed weekly with corn oil vehicle (n 5 5) or 200 mg
bisphenol A [purity not indicated] (n 5 12). [The
specific method of oral dosing was not reported. It is
assumed that birds were dosed until they were killed.]
Chickens were killed at 16 weeks of age. Combs and
testes were weighed. Testes were fixed in 4% paraformaldehyde
and examined histologically. [Statistical
methods were not discussed, and the levels of statistical
significance were not reported.] Bisphenol treatment
did not affect body weight, but comb and testis
weight were significantly lower in the chickens exposed
to bisphenol A. Spermatogenesis was disturbed in the
chickens of the bisphenol A group, as observed by small
seminiferous lumen and scarcity of spermatids and
mature sperm. Diameter of seminiferous tubules and
incidence of seminiferous tubules with mature sperm
were significantly lower in the bisphenol A group. The
study authors concluded that bisphenol A might disturb
the growth of comb and testes in male chickens, possibly
through an endocrine mechanism.
Strengths/Weaknesses: The study of male puberty in
chickens is a strength. Weaknesses are the use of a single
dose level and the lack of information on dosing and
statistical analysis. The study would have been strengthened
by measurement of hormone levels.
Utility (Adequacy) for CERHR Evaluation Process:
This study is not useful to the evaluation process.
Sashihara et al. (2001), supported by the Japan Ministry
of Education, Science, and Culture and the Uehara
Memorial Foundation, examined the effects of early life
exposure to bisphenol A on growth and behavior in male
chicks. Layer type (Julia) chicks were obtained from a local
hatchery, housed in windowless rooms [no further
housing details provided], given ad lib access to water
and feed (Toyohashi Feed and Mills Co.), and provided
continuous lighting. Birds were group housed based on
weight. At 4 days of age, 0, 100, or 200 mg of bisphenol A
[purity not given] dissolved in 10% ethanol and sesame
oil, was injected into the brain (n 5 12 or 13 per group).
Chicks were followed for growth up to 20 days after
treatment. A subset of 7 chicks/group was used for
behavioral testing 8 days after treatment. Birds were
placed under isolation distress condition and for a 5-min
period were observed in a cage for motor activity and
vocalization. At 20 days of age, birds were killed and liver,
kidney, testis, and brain were weighed. Statistical analyses
were performed using ANOVA and Duncan multiple
range tests.
There were no treatment effects on food intake 6 hr
after injection or on body weight gain measured 3 days
after exposure. In the behavioral test, there were no
treatment effects on jumping, locomotor activity, and
duration of crouching. There was a statistically significant
dose-dependent increase in the frequency of distress
vocalizations. There were no treatment effects at 20 days
on body or organ weights. The authors concluded that an
acute early life exposure of the chick brain to 100 or
200 mg bisphenol A may affect stress-induced behavior,
which may involve an estrogen-mediated pathway.
Strengths/Weaknesses: The rationale for the selection
of the test animal and dosing procedures are not
provided. Given that acute doses were injected directly
into the brain, specific rationale for the method and
selection of dose are critical to understanding the
relevance of the study to human health or to wildlife or
livestock concerns. This provides a vacuum for the
interpretation of the dose-related increase in vocalizations
that were reported.
Utility (Adequacy) for CERHR Evaluation Process:
This study is not useful to the evaluation process.
Furuya et al. (2006), supported by the Japanese
Ministry of Education, Science, Sports, and Culture,
examined the effects of bisphenol A exposure on
development of male chicks. Beginning at 2 weeks of
age, male white Leghorn chicks were orally dosed every
2 days with bisphenol A at 0 (alcohol/corn oil vehicle)
0.002, 0.020, 0.200, 2, or 200 mg/kg bw. The high-dose
level was considered to be a positive control based on
previous observations in the laboratory. [No information
was provided about the specific method of oral dosing,
number of birds treated, purity of bisphenol A, or the
type of feed or caging and bedding materials used. It
was implied but not clearly stated that exposures were
continued until the birds were killed.] The birds were
killed at 5, 10, 15, 20, and 25 weeks of age. The comb,
wattle, and testes were weighed. Part of the testicular
tissue was used to isolate mRNA for evaluation of ERa
and aromatase expression by RT-PCR. Additional testicular
tissue was fixed in 10% buffered formalin for
histopathology analysis and assessment of spermatogenesis
by using immunohistochemistry techniques to
measure proliferating cell nuclear antigen levels. [Methods
for statistical analyses were not reported.]
Although responses were not dose-related, significant
decreases in weight (doses at which effects were
observed) were reported for comb and wattle at 10
weeks of age (Z0.002 mg/kg bw), testis at 10 weeks of
age (200 mg/kg bw), comb and testis at 15 weeks of age
(Z0.020 mg/kg bw), wattle at 15 weeks of age (Z
0.2 mg/kg bw), comb at 20 weeks of age (Z0.200 mg/
kg bw), testis at 20 weeks of age (200 mg/kg bw), and
comb and testis at 25 weeks of age (200 mg/kg bw).
There were no effects on body weight. Histopathological
observations in testis (doses at which effects were
observed) included significant and dose-related reductions
in the number of spermatogonia at 5 weeks of age
(Z 2 mg/kg bw) and number of spermatogonia, spermatocytes,
and spermatids at 10–25 weeks of age
(Z0.02 mg/kg bw, except for decreases in spermatocytes
at 10 weeks of age, which occurred at Z0.200 mg/kg
bw). Seminiferous tubule diameter was significantly
reduced at all ages in groups exposed to Z0.020 mg/kg
bw. Significant and dose-related reductions in testicular
proliferating cell nuclear antigen levels were observed at
Z0.200 mg/kg bw at 10 weeks of age and Z0.020 mg/kg
bw at 15–25 weeks of age. ERa mRNA was significantly
increased according to dose (doses at which effects were
observed) at 10 weeks of age (Z0.020 mg/kg bw), 15 and
20 weeks of age (Z0.200 mg/kg bw/day), and 25 weeks
of age (200 mg/kg bw). Significant and dose-related
increases were also observed for aromatase mRNA
expression (doses at which effects were observed) at 5
weeks of age (Z0.002 mg/kg bw), 10 weeks of age
(0.200 mg/kg bw), and 15 weeks of age (200 mg/kg bw).
The study authors concluded that exposure to bisphenol
A at environmentally relevant levels may affect male
chicken phenotypes and result in unbalanced gene
expression in the testis.
Birth Defects Research (Part B) 83:157–395, 2008