'Map-reading' for male mice falls foul of BPA
A study looking into the potential effects of Bisphenol A (BPA) - a compound widely used in plastics, which has long-been associated with concerns over its estrogenic properties - has confirmed the existence of gender-bending traits amongst BPA-exposed deer mice. The work, which is soon to be published in the Proceedings of the National Academy of Sciences, comes from a University of Missouri group, led by Prof. Cheryl Rosenfeld. The results could point to what maybe happening to developing unborn children, who are exposed to BPA whilst in the womb.
Deer mice were seen as a good test candidate for this area of research, because they have easily tested differences in behavior between the sexes. For the guys, good 'map-reading skills' - or rather enhanced 'spatial navigational abilities' - are essential in helping them to find a mate in the wild. In contrast, the female deer mice, who are content to wait for suitors to seek them out, are pretty poor at finding their way around. That's a strong, and eerily familiar, gender difference that the team could test for.
The mothers of some of the mice to be tested were fed a diet, which was contaminated with BPA - but at levels below those that the US FDA (Food and Drug Administration) has said are safe for pregnant mothers. Once the male deer mice were sexually mature, they were then tested, by letting them loose in a maze, and recording their efforts to get out. It was quickly shown that the males who were bombarded with BPA whilst in the womb, suffered from a crippling sexual defect - becoming unable to navigate their way to potential female mates.
That strongly hints at a demasculinization of the male deer mice - especially as the researchers also noticed a distinct lack of interest from the female mice, towards the BPA-exposed males. Rosenfeld said 'Females do not want to mate with BPA-exposed male deer mice, and BPA-exposed males perform worse on spatial navigation tasks that assess their ability to find female partners in the wild.'
Such effects are consistent with health worries about BPA - and already, many countries, including Canada and some US states, have banned BPA containing products from baby bottles and feeding equipment. And a recent University of California study showed that 96% of pregnant women contained BPA in their blood. The paper's lead author recognizes these concerns, but sees the need for more research.
'These findings presumably have broad implications to other species, including humans, where there are also innate differences between males and females in cognitive and behavioral patterns,' Rosenfeld said. 'In the wide scheme of things, these behavioral deficits could, in the long term, undermine the ability of a species such as the deer mouse to reproduce in the wild. Whether there are comparable health threats to humans remains unclear, but there clearly must be a concern."
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