Female rats that are exposed to PCBs in the womb are reluctant to mate as adults. This raises the possibility that similar chemical contaminants can cause low sex drives in women.
PCBs are a group of stable chemical additives once widely used in the production of pesticides, lubricants and plastics. Their use was banned in many countries after it became clear that some PCBs mimic hormones. But there is strong evidence that PCBs are still widespread in the environment. The food crisis that struck Belgium in June was partly caused by PCB contamination of poultry and dairy produce.
Zoologists Yu-Wen Chung and Lynwood Clemens of Michigan State University in East Lansing tested the effects on rats of two commercial PCBs, Aroclor 1221 and 1254. A1221 is known to mimic oestrogen and A1254 is thought to reduce dopamine levels in the brain.
They injected 40 pregnant rats with either pure sesame oil or a mixture of oil and the PCBs, first on day 14 of gestation, then on the day of the pup's birth and again 10 days later while the pups were suckling. Two months later, Chung and Clemens looked at the sexual behaviour of the female offspring.
"Female rats normally adopt a stereotypical posture when copulating, raising their back and hindquarters to help the male mate," says Chung. But rats exposed to A1221 did not indulge in this sexual come-on nearly as often as rats exposed to A1254 or those that had not been exposed to either PCB.
A second test paired female and large male rats in a cage with two compartments. If the females didn't feel like mating, they could escape into the second chamber through a hole too small for the larger frustrated males to follow.
It turned out that females exposed to A1221 left the males more often
and took longer to return after each copulation attempt by the males (Bulletin
of Environmental Contamination and Toxicology, vol 62, p 664). "We found that
females stayed away
Contact: Claire Bowles