OncologyBPA May Cause Heart Disease In Women, Said Scientists Studying Rats
A team of scientists in the US suggested that bisphenol A (BPA) may harm the heart, particularly in women, because of what they discovered in tests
on female rats and mice. BPA is a chemical used in the manufacture of polycarbonate, a hard clear plastic used to make food containers, among other
things.
The findings are of studies by scientists at the University of Cincinnati (UC) in Ohio, and are being presented at ENDO 09, the Endocrine Society"s
annual meeting that is taking place June 10-13 in Washington DC this year.
The researchers found that exposure to BPA or estrogen or both made the hearts of female rats and mice behave abnormally.
They also found that estrogen receptors are responsible for the effect.
One of the lead investigators, Dr Scott Belcher, from UC"s department of pharmacology and cell biophysics, told the press that:
"There is broad exposure to bisphenol A, despite recognition that BPA can have harmful effects."
"We had reason to believe that harmful cardiovascular affects can be added to the list," he said.
Other studies have linked BPA, described as an "environmental pollutant with estrogen activity" to neurological defects, diabetes and breast and
prostate cancer, said the authors.
For their research, Belcher and colleagues used live cultures of cells taken from rat or mouse hearts, briefly exposed them to BPA on its own, BPA
with estrogen, and estrogen alone.
They found that both compounds caused significant changes in the activity of cardiac muscle cells from the females but not from the males.
In further studies they found that these cellular changes led to an increase in irregular heart beating in the female hearts.
"Low doses of BPA markedly increased the frequency of arrhythmic events," said Belcher.
"The effect of BPA on these cardiac arrhythmias was amplified when exposed to estradiol, the major estrogen hormone in humans," he
added.
Belcher and colleagues then investigated the effect using cellular imaging.
They found that BPA, estrogen, or both altered the concentrations of free calcium in the heart cell which rapidly stimulated contraction, but this only
happened in cardiac muscle cells from females.
"BPA"s presence increased the frequency of calcium "sparks" from the sarcoplasmic reticulum -- the part of the cardiac muscle that stores and releases
calcium ions -- indicating spontaneous release or "leak" that"s likely causing the heart arrhythmias and may have other harmful actions, especially
following heart attack," explained Belcher.
They also looked at the underlying mechanisms that make cardiac muscle cells respond to estrogen and BPA.
Using selective estrogen receptor drugs in animals bred without estrogen receptors, they found that estrogen has different actions in cardiac cells of
females and males.
"In female cardiac muscle cells, the blocking or genetic removal of estrogen receptor beta completely blocked the contractile effects of BPA and
estrogen, while in males, blockade of the effects of estrogen receptor alpha caused the male heart to become more "female-like" and become responsive
to estrogen and BPA," said Belcher.
"These studies have identified new and important potential cardiac risks associated with BPA exposure that may be especially important for women"s
heart health," he added.
The research was funded by the National Institutes of Health and the UC Center for Environmental Genetics.
University of Cincinnati Academic Health Center.
Written by: Catharine Paddock, PhD
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