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

Endpoint b
BISPHENOL A 301
Table 80
Behavior of Female Mice After Gestational and Lactational Exposures a
Bisphenol A, mg/kg bw/day
2 200 Ethinyl estradiol
Puberty onset 2 k 4.5 days k 6.25 days
Time in open arms of plus maze 2 k 41% (P 5 0.06) k 73%
Time in light part of light/dark preference box 2 k 52% k 69%
Errors in radial arm and Barnes mazes 2 2 k
a Ryan and Vandenbergh (2006).
b The size of the difference from control was estimated from graphs.
k Statistically significant decrease from control value; 2 no statistical difference from control value, kdecrease identified by authors
although statistical difference from control not shown.
estradiol at 3 mg/kg bw/day by gavage. The compounds
were administered 3 times a day from the mating period
through weaning of offspring. Seven male offspring/
group were examined in a place-conditioning test at 7
weeks of age. During the preconditioning period, mice
were placed in one compartment of a cage following
injection with saline and in another compartment of the
cage following s.c. injection with morphine. During
testing, the amount of time spent in each compartment
of the cage was measured. Statistical analyses included
ANOVA followed by Bonferroni/Dunnett test. [It was
not clear if the litter or offspring was considered the
statistical unit.]
Developmental exposures to either bisphenol A dose
resulted in a preference for the cage compartment
associated with morphine exposure. Developmental
exposure to 17b-estradiol at 3 mg/kg did not affect place
preference. Based on the findings of this study and in
vitro studies described in Section 3.2.1.1, the study
authors concluded that bisphenol A alters dopamine
responsiveness in mouse neurons and astrocytes, which
could potentially contribute to development of psychological
dependence on drugs of abuse.
Strengths/Weaknesses: Strengths include the use of a
positive control and corresponding measurement of in
vitro and behavioral endpoints. Weaknesses include the
use of only 2 doses, 1 very low and 1 high (both had
similar effects), inadequate experimental details regarding
exposure and numbers of dams, small sample size for
behavioral endpoints, inappropriate statistical procedures
that did not account for litter of origin or repeated
behavioral measurements.
Utility (Adequacy) for CERHR Evaluation Process:
This report is inadequate and not useful for the
evaluation process.
Ryan and Vandenbergh (2006), supported by North
Carolina State University and EPA, evaluated the effects
in mice of prenatal and postnatal exposure to bisphenol
A on sexually dimorphic behaviors. C57BL/6 mice were
maintained in polycarbonate cages (checked frequently
for condition) with chip bedding and were given Purina
5001 chow. Females were mated and the day a vaginal
plug was identified was considered GD 1. Beginning on
GD 3, dams were treated with bisphenol A [purity not
indicated] 2 or 200 mg/kg bw/day, ethinyl estradiol 5 mg/
kg bw/day, or the tocopherol-stripped corn oil vehicle.
The dose was placed in the back of the throat with a
gavage needle. Daily dosing was continued to PND 21,
when pups were weaned. One female per litter was
Birth Defects Research (Part B) 83:157–395, 2008
randomly selected for behavioral testing and was
ovariectomized. Pup anogenital distance was
measured at weaning. Non-ovariectomized mice were
checked for vaginal opening and vaginal smears taken
daily thereafter. Puberty was defined as the first
day on which cornified cells were detected in 4–7
females/group. Fourteen mice/treatment group were
tested in an elevated plus maze and a light/dark
preference chamber. Sixteen mice/treatment group were
tested in a radial arm maze and a modified Barnes maze.
Testing occurred 2 weeks after ovariectomy. Statistical
analysis used ANOVA with post-hoc Student t-test. The
radial arm and Barnes mazes were run for 5 consecutive
days and a repeated measures design was added to the
ANOVA.
There was no effect of treatment on anogenital
distance or anogenital distance divided by body weight.
Other results are summarized in Table 80. Puberty was
advanced by exposure to ethinyl estradiol or the highdose
of bisphenol A. The results of the elevated plus and
light/dark preference tests led the authors to conclude
that bisphenol A and ethinyl estradiol increased anxiety.
The improved performance in the radial arm and Barnes
mazes led the authors to conclude that ethinyl estradiol
masculinized spatial ability. [The results from the
elevated plus maze also suggest masculinization of
behavior, because males show more ‘‘anxiety’’ in this
paradigm.] Bisphenol A 200 mg/kg bw/day resulted in a
decrease in errors on earlier trials than the control in the
radial arm maze, but this effect was not characterized by
the authors as providing strong evidence of an alteration
in spatial memory.
Strengths/Weaknesses: Selection of established measurements
of sexually dimorphic behaviors and replication
of previous work by Howdeshell et al. (1999), the use
of positive controls, the appropriate evaluation of
pubertal onset, adequate sample sizes for behavioral
methods, weight, and AGD measures are all strengths of
this work. A weakness is the small sample size for
evaluating pubertal onset.
Utility (Adequacy) for CERHR Evaluation Process:
This study is adequate and of high utility for the
evaluation process with the exception of the pubertal
data.
Tyl et al. (2006), sponsored by the American Plastics
Council, conducted a two-generation GLP study of
bisphenol A in CD-1 mice. [This study is discussed in
detail in Section 4.2.3.2. Results relevant to developmental
toxicity are presented here.] Mice were fed