“Not My Type,” Say Female Mice to Male Mice Exposed to BPA

BPA exposure in male deer males makes them less attractive to females
BPA exposure in male deer males makes them less attractive to females.

The bisphenol A (BPA) controversy on whether or not it’s dangerous rears its head again. Science and health writer Eryn Brown at the Los Angeles Times reports on a recent study in mice and how exposure to the chemical may affect the sexual attractiveness of males to females.

A team led by Cheryl Rosenfeld at the University of Missouri-Columbia looked at how deer mice changed in their behavior and cognition when exposed to BPA. In particular, they focused on sexual behavioral and cognitive traits that help the mice find and attract mates because these sexual behaviors are controlled by hormones.

The team predicted that sex hormones would be highly sensitive to BPA’s endocrine-disrupting property. To test out their hypothesis, Brown explains, they fed female deer mice three different diets: one doused in BPA, one enriched in the synthetic estrogen called enthinyl estradiol, and a third control diet that didn’t contain either chemical.

They then put the offspring of those mice, boys and girls, through tests designed to measure behaviors that would influence their ability to mate in the wild. Tests included finding their way around mazes, an approximation of how the mice would be able to get around in the wild and explore new territories for mates.

The researchers also compared the amount of time the females spent in “nose-to-nose contact” with control group versus BPA-exposed male mice (nose-to-nose contact in mice indicate female preferences in mates, kind of like kissing).

Male mice whose moms had eaten the BPA-enriched diets looked normal and had regular testosterone levels. But they had trouble figuring out how to navigate the mazes (which begs the question: were they truly navigationally challenged or even less prone to ask for directions?). This suggested to Rosenfeld and her colleagues that they would also have trouble finding their way around new territory in the wild and meeting new mice.

More interestingly, female mice spent less time nosing around the BPA-exposed males, which suggested that they found them less appealing.

But, as Brown explains in her story:

In and of itself, the discovery doesn’t shed direct light on the risk BPA poses to people. But Rosenfeld said the research could influence future studies on BPA’s impact on humans.

‘Investigators looking for obvious BPA-induced differences, such as chromosome deletions or DNA mutations, could be missing subtle behavioral differences that eventually lead to long-term adverse outcomes,’ she said, in a statement. ‘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. 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.’

Source: “Study: BPA exposure might make male mice undesirable to females,” Los Angeles Times, 06/27/11
Image by 6th Happiness, used under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.