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Bisphenol slecht voor hart en vruchtbare vrouwen*

Uit twee studies blijken weer eens de gevaren van bisphenol-A (BPA). De ene Duitse laboratoriumstudie laat zien dat Bisphenol in lichaamscellen calciumkanalen kan blokkeren en zo het samentrekken van spieren zoals hartspieren be´nvloeden als ook de communicatie tussen zenuwcellen. De tweede studie met resusapen, die qua voortplantingsorganen het meest op de mens lijken, laat zien dat BPA de vorming van eicellen be´nvloed en daardoor schade aan de chromosonen kan geven met alle mogelijk nare gevolgen voor eventuele nakomelingen.

BPA is een chemische stof die wordt gebruikt voor de productie van polycarbonaat, een transparante plastic die onder andere gebruikt wordt als drager van CD's en DVD's en voor onbreekbare flessen voor (baby)voeding, voor tafelbestek, en voorwerpen voor gebruik in microgolfovens. Het wordt ook gebruikt in epoxyharsen die als beschermende coating aan de binnenkant van voedingsverpakkingen in blik of karton worden aangebracht, of in leidingen en reservoirs voor drinkwater. Bisfenol A wordt ook gebruikt in vlamvertragende middelen, ook in tandvullingen en als oplosmiddel voor drukinkten en in thermisch papier. Het is bewezen dat BPA kan vrijkomen uit de verpakking en in de voeding terechtkomt.

Researchers discover adverse effects of Bisphenol A on calcium channels
Bisphenol A, a substance found in many synthetic products, is considered to be harmful, particularly, for fetuses and babies. Researchers from the University of Bonn have now shown in experiments on cells from human and mouse tissue that this environmental chemical blocks calcium channels in cell membranes. Similar effects are elicited by drugs used to treat high blood pressure and cardiac arrhythmia. The results are now presented in the journal Molecular Pharmacology.
The industrial chemical bisphenol A (BPA) is worldwide extensively utilized for manufacturing polycarbonates and synthetic resins. "This substance has been shown to affect the hormonal system and may have negative effects on the function of enzymes and carrier proteins," reports Prof. Dr. Dieter Swandulla from the Institute of Physiology II at the University of Bonn. BPA is associated with heart disease, diabetes, obesity, cancer, and neurological dysfunction. "It seems that fetuses and newborns are particularly sensitive to BPA," adds the physiologist. Due to its unpredictable effects, the EU Commission banned the use of BPA in baby bottles in 2011 as a precaution.
Bisphenol A blocks multiple essential calcium channels
The team of researchers around Prof. Swandulla now reports that BPA reversibly blocks calcium channels essential for cell function in mouse and human cells. Calcium ions flowing through these pore-like so-called channel proteins into living cells, control e.g. the contraction of heart muscle cells, the activity of enzymes, and the communication of nerve cells with each other. "Drugs such as those used to treat high blood pressure and cardiac arrhythmia on the one hand, and neurotoxins, such as heavy metals, on the other hand act on exactly the same calcium channels," explains the physiologist from the University of Bonn. "This indicates that BPA can indeed have adverse effects on human health." Since BPA binds to the calcium channels reversibly, there is at least the possibility of the chemical being eliminated from the body. 
Bisphenol A and its derivatives are ubiquitous
Nowadays BPA and its related substances can be detected almost everywhere in the environment. Effective doses are found in CD's, paper money, thermal paper, food cans, dental fillings and flame retardants, even in the breathing air and in house dust. Humans are meanwhile chronically exposed to these compounds. "This is why it would be desirable to completely stop the production of BPA," says Prof. Swandulla. "Due to the high-volume production and its widespread occurrence, it would, however, take a very long time to remove this chemical from the environment and the human organism." Consequently, alternatives to BPA should be utilized which are harmless to humans and other organisms.
More information: Bisphenol A inhibits voltage-activated Ca2+ channels in vitro: mechanisms and structural requirements, Molecular Pharmacology, DOI: 10.1124/mol.112.081372

De studie. Provided by University of Bonn


Primate Study Adds to Evidence of BPA Harming Human Reproduction
A Washington State University researcher has found new evidence that the plastic additive BPA can disrupt women's reproductive systems, causing chromosome damage, miscarriages and birth defects.
Writing in the journal Proceedings of the National Academy of Sciences, WSU geneticist Patricia Hunt and colleagues at WSU and the University of California, Davis, report seeing reproductive abnormalities in rhesus monkeys with BPA levels similar to those of humans. By using an animal with the most human-like reproductive system, the research bolsters earlier work by Hunt and others documenting widespread reproductive effects in rodents.
"The concern is exposure to this chemical that we're all exposed to could increase the risk of miscarriages and the risk of babies born with birth defects like Down Syndrome," says Hunt. "The really stunning thing about the effect is we're dosing grandma, it's crossing the placenta and hitting her developing fetus, and if that fetus is a female, it's changing the likelihood that that female is going to ovulate normal eggs. It's a three-for-one hit."
The research also adds to the number of organs affected by BPA, or bisphenol A, which is found in plastic bottles, the linings of aluminum cans and heat-activated cash register receipts. This May, Hunt was part of another paper in PNAS reporting that the additive altered mammary development in the primate, increasing the risk of cancer.
Hunt's colleagues at UC, Davis exposed different groups of gestating monkeys to single daily doses of BPA and low-level continuous doses and looked at how they affected the reproductive systems of female fetuses. She saw that in the earliest stage of the adult's egg development, the egg cell failed to divide properly. Earlier mouse studies showed similar disturbances translated into genetic defects in the mature egg.
A fertilized egg with the wrong number of chromosomes will almost always fail to come to term, leading to a spontaneous abortion or progeny with birth defects.
In monkeys exposed continuously, Hunt saw further complications in the third trimester as fetal eggs were not packaged appropriately in follicles, structures in which they develop. Eggs need to be packaged properly to grow, develop and mature.
"That's not good," says Hunt, "because it looks to us like you're just throwing away a huge number of the eggs that a female would have. It raises concerns about whether or not she's going to have a really short reproductive lifespan." (December 2012)


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