BPA can adversely affect circadian rhythms in the pups of pregnant mice that have been exposed to the substance before birth, according to preliminary study results presented at a meeting in the US on 25 March.
Various biological processes exhibit oscillations with 24 hour periodicity, resulting in so-called circadian rhythms, which are linked to patterns of sleep and activity.
In the study, which has yet to be published, scientists at the University of Calgary in Canada fed BPA-laden food to pregnant mice.
Then, when the pups were 12 weeks old, the scientists tested how the sleep and activity patterns of the pups responded to changes in the patterns of light and darkness of their environment.
The pattern was 12 hours of light followed by 12 hours of darkness for four weeks. Then, it was changed to a 24-hour dark cycle with irregular pulses of light, for the following four weeks.
The light pulses tested the responsiveness of the circadian rhythms to unexpected stimuli.
The pups exposed to BPA during gestation exhibited alterations in their daily patterns, and the timings of activity, indicating disrupted circadian signalling, said Deborah Kurrasch, who is leading the research. The adverse effects were more pronounced when the animals were placed in 24-hour darkness.
Professor Kurrasch presented the preliminary results at the annual meeting of the Endocrine Society held in New Orleans. She said that the effects on circadian rhythms could be a contributing factor to previously observed hyperactivity in BPA exposed mice.
Four generations
At the same meeting, David Lopez Rodriguez, a graduate student at the University of Liège, Belgium, presented preliminary results from a different study suggesting EDCs can adversely affects rats across four generations.
In the study, which, like the BPA study, has yet to be published, the scientists gave pregnant rats (F0 rats) food containing a mixture of 13 known EDCs, including plasticisers, biocides and UV filters. They identified adverse effects in the pups (F1 rats) and in the pups of two subsequent generations (F2 and F3 rats).
There were affects on sexual development in the F2 and F3 rats, including delayed puberty, but not in the F1 rats. There were, however, effects on the maternal care activity of the F1 rats, which for example spent less time licking their pups, a behaviour known to be transmitted through generations. Additionally, in the hypothalamus area of the brain, the expression and organisation of genes involved in puberty and reproduction were affected.
Mr Lopez Rodriguez said the results were consistent with the recent discovery that the environment can affect gene expression through changes in the organisation of DNA – epigenetic changes.
ACC
“Without a detailed description of the methodologies used and no access to the data, one cannot determine if a study has produced any meaningful results,” said a spokesperson for the American Chemistry Council. “The vast majority of the endocrine active substances that scientists have studied to date have not been demonstrated to cause adverse health effects at typical exposures as a consequence of endocrine activity.”