Exposure to Endocrine Disruptors during Pregnancy Affects the Brain Two Generations Later
Prenatal exposure to low doses of the environmental contaminants polychlorinated biphenyls, or PCBs, change the developing brain in an area involved in metabolism, and some effects are apparent even two generations later, a new study finds. Performed in rats, the research
was presented at the Endocrine Society’s 97th annual meeting
in San Diego.
Hereditary effects included increased body weight,
but only in descendants of females—and not males—exposed to PCBs in the
womb, said study co-author Andrea Gore, PhD, professor at the University
of Texas at Austin.
“These endocrine-disrupting chemicals affect the developing brain differently in males and females,” Gore said.
are known endocrine disruptors, chemicals in the environment that
interfere with hormones and their actions in the body. PCBs are present
in air, water, soil and many products manufactured before these
chemicals were banned in the U.S. in 1979.
Brain development and function, and their regulation by hormones, are very similar between rats and humans, according to Gore.
believe,” Gore said, “that results in our rat model may point to the
potential vulnerability of the developing human brain to environmental
In this study, funded by the National
Institutes of Health, the investigators gave a mixture of PCBs to
pregnant rats at the beginning of their third trimester, thus directly
exposing their offspring to the endocrine disruptors. Doses of PCBs were
low to be comparable to that of human exposure, Gore said. Other
pregnant rats received a low dose of estrogen to account for PCB’s
estrogenic effects, and control rats received a placebo instead of PCBs.
researchers allowed the first-generation rats born to PCB-exposed and
control rats to mature and then bred them (both males and females)
through two additional generations, to see if the effects of PCBs were
Gore and her colleagues found that the first generation
of PCB-exposed rats had changes to 9 genes in their brains, in the
arcuate nucleus, a region involved in reproduction and metabolic
function. The researchers saw few changes in the second-generation
rodents, other than decreased levels of the hormone progesterone in
In the third generation, though, rats descended from
animals exposed to the low-dose estrogen had changes to three genes in
the arcuate nucleus that are involved in biological rhythms and
metabolic function. These changes did not occur in descendants of
Because the third generation had no personal
exposure to the treatment, the researchers concluded that the observed
changes occurred through some form of inheritance. Gore said the reason
why the second generation was less affected than the third generation is
unclear but may have to do with the timing of the original exposure
All three generations of rats descended from
PCB-exposed females weighed significantly more than the other rats, the