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

the studies. In each study, ddY mice received feed
containing bisphenol A from mating to weaning of their
offspring. [No information was provided on purity of
bisphenol A, type of feed, caging and bedding
materials, the number of dams treated, or the ages or
sexes of offspring that were tested.] Statistical analyses
included ANOVA with Bonferroni/Dunnett test. [It was
not clear if the litter or offspring was considered the
statistical unit.] In a place conditioning-study, testing
was conducted in 6–14 mice/group born to dams
exposed to bisphenol A at 0, 0.03, 0.3, 3, 500, or
2000 mg/kg food. [Assuming a female mouse eats
B0.2 kg feed/kg bw/day (USEPA, 1988), bisphenol A
intake would have been 0.006, 0.06, 0.6, 100, or 400 mg/
kg bw/day.] During the preconditioning period, mice
were placed in one section of a cage following injection
with saline [specific route not reported] and in another
section of the cage following s.c. injection with 1 mg/kg
bw morphine. On the day of testing, the amount of time
spent in each section of the cage was recorded. Mice from
the lowest dose group (0.03 mg/kg food) and 2 highest
dose groups (500 and 2000 mg/kg) food spent more time
in the section of the cage associated with morphine
injection. [Compared to controls, the time spent in the
morphine-associated section of the cage was B9.5-, 7-,
and 9-fold longer in each of the respective dose
groups.] Total locomotor activity was measured for 3 hr
in 5–15 mice/group born to dams exposed to 0, 0.03, 3, or
2000 mg/kg food. Following s.c. injection with 10 mg/kg
bw morphine, activity was increased in mice from the
low- (0.03 mg/kg food) and high- (2000 mg/kg food)
dose groups compared to the control group [increased
by B9-fold in the low dose group and 12-fold in the
high-dose group]. Binding of 35 S-guanosine-5 0 [g-thio]triphosphate
in the limbic system was measured in 3
samples/group obtained from offspring of dams exposed
to 0.03, 3, or 2000 mg/kg food. Dopamine-induced
binding of 35 S-guanosine-5 0 [g-thio]-triphosphate in the
limbic system was increased at each dose level compared
to controls [by B32, 18, and 56%]. Based on their
findings, the study authors concluded that prenatal and
neonatal exposures to low bisphenol A doses can
potentiate central dopamine receptor-dependent neurotransmission
in the mouse.
Strengths/Weaknesses: This study is so poorly written
that it is extremely difficult to understand many
sentences (let alone paragraphs) and to determine
precisely what was done, why, and what happened.
The main weakness of the study is therefore its inability
to pass its message to the reader. Given this limitation, it
is difficult to determine whether the study has any
strengths, and if so what they might be.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process
because of the lack of methodological details and the
poor communication of the study results.
Kawai et al. (2003), supported by Core Research for
Evolutional Science and Technology and Japan Science
and Technology, examined the effects of prenatal bisphenol
A exposure on aggressive behavior in male mice.
[No information was provided about feed, bedding, or
caging materials.] Pregnant CD-1 mice were randomly
assigned to groups of 7 and orally dosed by micropipette
with 0.002 or 0.020 mg/kg bw/day bisphenol A [purity
not reported] on GD 11–17. A control group of 9 mice
Birth Defects Research (Part B) 83:157–395, 2008
BISPHENOL A
289
received the corn oil vehicle by micropipette during the
same time period. Doses were said to be within the range
of human exposures. Pups were weaned on PND 21 (day
of birth 5 PND 0), and males randomly selected males
from the same litter were housed in groups of 4 or 5.
Aggression testing was conducted at 8, 12, and 16 weeks
of age. For the testing, 15 control male mice from the 9
litters were randomly selected to be opponents and
housed 5/cage. Opponents were used only once/day for
testing. During testing of mice from the control and
treated groups, the subject was housed alone for 5 min
before placing the opponent mouse into the cage.
Behavior with the opponent mouse was observed for
7 min. The numbers of mice evaluated were 26–32/group
at 8 weeks of age, 18–24/group at 12 weeks of age, and
10–16/group at 16 weeks of age. MiceRandomly selected
were killed at 9, 13, and 17 weeks of age, 1 week
following behavior testing, for measurement of testis
weight and serum testosterone level. [The results section
states that testis weights and serum testosterone levels
were obtained at 8, 12, and 16 weeks of age.] Eight
mice/group were killed after the first 2 test periods and
10–16 mice/group were killed after the last test period.
Mice that were not killed were tested at the next
evaluation period, so that mice killed after 16 weeks of
age were tested a total of 3 times. Statistical analyses
included ANOVA and Spearman rank correlation test. [It
does not appear that the litter was considered the
statistical unit.]
Aggression scores, as determined by contact time,
were increased significantly compared to the control
group at 8 weeks of age in both the low- (124% increase)
and high- (146% increase) dose bisphenol A groups. No
treatment-related effects on aggression score were
observed at 12 and 16 weeks of age. In the low-dose
group, relative (to body weight) testis weight was 10%
lower than controls at 8 weeks of age and 18% lower than
controls at 12 weeks of age. Relative testis weight was
11% lower than control values in the high-dose group at
12 weeks of age. No significant effects were observed for
serum testosterone levels. There were no correlations
between serum testosterone levels and contact time in
aggression testing. The study authors concluded that
prenatal bisphenol A exposure of mice resulted in
behavioral changes and decreased relative testis weight
that was more pronounced at the lower dose.
Strengths/Weaknesses: Strengths are the use of 2 low
dose levels and the oral route of administration. The lack
of husbandry information, inappropriate presentation of
testis weight data, variable degrees of repeated behavioral
testing, and the apparent lack of consideration of
possible litter effects are weaknesses.
Utility (Adequacy) for CERHR Evaluation Process:
This study is inadequate for the evaluation process due
to the reasons stated above.
Kawai et al. (2007), supported by Japan Sciences
Technology and Core Research for Evolutional Science
and Technology, evaluated the brain expression of ERa
and ERb in male mice exposed in utero to bisphenol A.
Pregnant ICR mice were fed bisphenol A in corn oil by
micropipette on GD 11–17 at 0 or 0.002 mg/kg bw/Day 9,
n 5 18/group). Mice were housed singly in polypropylene
cages. [The first day of gestation was likely
designated as GD 0, according to a figure. Type of
feed and bedding material were not given.] Litters were