29 June 2009

BPA exposure during pregnancy alters offspring's DNA

by Kate Melville

In animal studies, exposure to bisphenol A (BPA - a common chemical found in many plastic household items) during pregnancy is known to cause fertility defects in the offspring, and now researchers have told The Endocrine Society's 91st Annual Meeting in Washington how those defects occur.

The new findings join a growing body of animal research showing the toxic health effects of BPA, including reproductive and developmental problems. BPA is used to make hard polycarbonate plastic, such as for baby bottles, refillable water bottles and food containers, as well as to make the linings of metal food cans. It has estrogen-like properties and has been linked to female infertility in animals.

"The big mystery is how does exposure to this estrogen-like substance during a brief period in pregnancy lead to a change in uterine function," said study co-author Hugh Taylor, at Yale University School of Medicine. To tray and answer that question, Taylor injected pregnant mice with a low dose of BPA on pregnancy days 9 to 16. After the mice gave birth, the scientists analyzed the uterus of female offspring and extracted DNA.

They found that BPA exposure during pregnancy had a lasting effect on one of the genes (HOXA10) that is responsible for uterine development and subsequent fertility in both mice and humans. Furthermore, these changes in the offspring's uterine DNA resulted in a permanent increase in estrogen sensitivity.

The permanent DNA changes in the BPA-exposed offspring were not apparent in the offspring of mice that did not receive BPA injection (the controls). This finding demonstrates that the fetus is sensitive to BPA in mice and likely also in humans, Taylor says. "We don't know what a safe level of BPA is, so pregnant women should avoid BPA exposure. There is nothing to lose by avoiding items made with BPA - and maybe a lot to gain."

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Source: The Endocrine Society