WHEN does a female mouse behave like a male? When you give it small doses of bisphenol A, a chemical that mimics the hormone oestrogen. The 鈥済ender bender鈥�, which masculinises the brains of female mice, is the base chemical for making polycarbonate plastics, often used in bottles and food containers.
When Ana Soto and colleagues at Tufts University in Boston constantly infused bisphenol A into the tissue of pregnant and breastfeeding mice, the female pups displayed the masculinised effects. The doses were equivalent to concentrations found by the US Centers for Disease Control and Prevention in samples of human urine. 鈥淲e鈥檙e talking about environmentally relevant levels of exposure,鈥� says Soto.
The female pups of mice exposed to the chemical had half the normal number of neurons in an area which controls female reproductive cycles, the same number as males. They also performed more like males in a standard behavioural test (Endocrinology, DOI: 10.1210/en.2006-0189).
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Steven Hentges of the American Plastics Council in Arlington, Virginia, points out that humans can metabolise bisphenol A, whereas the mice could not do this since the chemical was administered direct to tissue. 鈥淚t makes you wonder if it鈥檚 relevant to humans,鈥� he says.
