Missouri: Biparental care of offspring, or care that is administered by both parents, occurs in only a minority of species, including humans. Past studies have shown that maternal care can be negatively affected when females are exposed to widely prevalent endocrine-disrupting chemicals including Bisphenol-A (BPA); however, no studies have shown how this chemical can affect maternal and paternal care when both parents are exposed. Now, researchers at the University of Missouri have used the monogamous, biparental California mouse species to prove that offspring born to parents who are exposed to BPA receive decreased parental care by both the mother and father.
Scientists believe results
could have relevance to human parenting as well.
The California mouse is used as a model for examining parental
behaviors because they are monogamous and, much like humans, both male
and female partners contribute to child-rearing. Male partners exhibit
cooperative care of the pups from birth to weaning by cleaning, grooming
and providing warmth by huddling over their young when females leave
the nest. Impaired care could lead to adverse consequences for the young
and, since brain regions and hormones regulating biparental behaviors
appear to be similar across species, this study may have human
“Endocrine-disrupting chemicals like BPA mimic the steroid hormones
that establish the ‘circuitry’ for the adult female brain during early
development, but little was known about how this chemical might affect
the father’s behavior,” said Cheryl Rosenfeld, associate professor of
biomedical sciences in the College of Veterinary Medicine and a researcher in the Bond Life Sciences Center at MU.
“Our study set out to address this critical void by exposing both males
and females to the endocrine-disrupting chemicals BPA and Ethinyl
estardiol (EE), the main active component of birth control pills, and
examine the repercussions of rearing offspring.”
For the study, researchers developmentally exposed female California
mice to one of three diets. One contained BPA, the second contained
concentrations of EE and the third was free of endocrine disruptors.
Likewise, males were developmentally exposed to the same three diets.
Then, the male and female mice were randomly paired. Since California
mice are monogamous, one male was paired with a single female for the
duration of the study. After being paired, parents and offspring were
observed for a variety of behaviors such as time the females spent
nursing the pups, male and female grooming of the pups and time spent in
and out of the nest by both parents. Throughout the study, development
of the pups, including body weight gain and temperature, was observed.
“The nature and extent of care received by an infant is important
because it can affect social, emotional and cognitive development,”
Rosenfeld said. “We found that females who were exposed early on to BPA
spent less time nursing, so the pups likely did not receive the normal
health benefits ascribed to nursing. Likewise, we found that
developmental exposure of males and females to these
endocrine-disrupting chemicals resulted in their spending more time out
of the nest and away from their pups, further suggesting that biparental
care was reduced.”
Findings also suggest that females can tell whether or not the male
is compromised by BPA and adjusts her parental care accordingly. These
females, although never exposed to BPA or endocrine disruptors, nursed
their pups less and spent more time outside the nest. Researchers
believed this was in response to whether her male partner was
developmentally exposed to one of the endocrine-disrupting chemicals,
said Sarah Johnson, a graduate student and lead author of the study.
The study, “Disruption of Parenting Behaviors in California Mice, a
Monogomous Rodent Species, by Endocrine Disrupting Chemicals,” was
funded by the National Institutes of Health (Grant: 5R21ES023150-02) and
was published in the journal PLOS One. The content is solely
the responsibility of the authors and does not necessarily represent the
official views of either funding agency.