did they do?
What did they find?
What does it mean?
et al. demonstrate that bisphenol A contamination at low
levels in the womb causes significant alterations in the development
of the rat prostate. Their study is especially valuable because
it provides detailed microscopic information about the ways that
low-level bisphenol A (BPA) affects prostate structure.
results demonstrate that rats exposed to BPA in the womb experience
alterations in cell function within the prostate at puberty. Some
of the changes resemble conditions in the human prostate that enhance
the potential of a nascent prostate cancer tumor. Hence these
results point toward the potential involvement of in utero
exposure to bisphenol A and other environmental
estrogens in prostate cancer.
did they do? Ramos et al. exposed fetal mice to bisphenol
A via osmotic pumps implanted in female rats during pregnancy. BPA
was delivered from day 8 of pregnancy through to delivery (day 23)
at either 25 µg/kg female body weight (parts per billion)
or 250 µg/kg. They then compared the exposed males to a control
group with respect to a series of microscopic
measurements and immunochemical assays in different tissues within
did they find? The prostates of males exposed in the womb were
significantly different from unexposed males by the time of puberty,
at both exposure levels used in the experiment. The differences
involved changes in structure, changes in the distribution of androgen
receptors, and alterations in immunohistochemistry of different
dot indicates a significant difference from control
of the protein vimentin increased in treated animals compared
to controls. In untreated animals, cells expressing vimentin
form a discontinuous ring in the periductal region of the prostate.
In BPA-treated animals, however, the vimentin+ cells formed
a "continuous uniform halo around the proximal and distal
of a-SMA decreased in treated animals. In untreated animals,
cells expressing this protein form a continuous ring around
the ducts. Following BPA treatment, the ring becomes discontinuous.
percentage of prostate stromal cells testing positive for androgen
receptors decreases following BPA treatment.
percentage of epithelial cells expressing
the enzyme prostate acidic phosphatase (PAP) decreased in BPA
does it mean? These findings show that prenatal exposure to
low, environmentally relevant doses of BPA induces abnormalities
in the development of the rat prostate, with effects observable
after puberty. Tissue organization and protein expression are altered.
Fewer androgen-sensitive cells are present. The structural changes
involve changes in the differentiation pattern of the periductal
stromal cells of the rat ventral prostate: BPA-treated animals develop
a thick layer of vimentin-positive and a-SMA-negative cells
in the periductal zone.
humans, alterations in the stroma appear to enhance the invasive
and/or malignant potential of a new tumor (Grossfield
et al. 1998). The discoveries by Ramos et al.
about low-level bisphenol A impacts on stromal cells in the rat
ventral prostate should lead to intensified research on the links
between BPA and human prostate cancer, and immediate reductions
in human exposure to BPA as a precautionary measure.
asserts that decades of experience with BPA demonstrates its safety.
Over those decades, manyprobably millionsof human fetuses
have been exposed to BPA and other environmental estrogens. In the
latter half of the 20th century in the US, the incidence of prostate
cancer increased significantly. No epidemiological study with the
data necessary to carry out a plausible test has ever (as of 1 January
2002) examined the potential link between prostate cancer and environmental
estrogen exposure in the womb. Hence industry's claim about the
demonstrated safety of BPA is clearly false.