Researchers from the University of Michigan measured free and conjugated bisphenol A (BPA) in human fetal livers retrieved from voluntary early pregnancy terminations (Nahar et al. 2012). Overall BPA levels were found to be higher in fetuses than in the two adult references. Further, they found reduced gene expression of BPA metabolism related genes.
The researchers extracted free and conjugated BPA from 50 fetal liver tissues and compared them to one male and one female adult control. Two adult liver samples were chosen as a reference in order to investigate differences in BPA metabolism between fetuses and adults. The adult metabolism is thought to eliminate BPA rapidly through conjugation reactions mainly in the liver. The free-to-conjugated BPA ratio illustrates how rapidly BPA is eliminated from the body.
The ratio of free-to-conjugated BPA in fetuses was above one, with more free BPA present than the rapidly excreted conjugated form.
Further, the researchers investigated differences in gene expression of BPA metabolism related genes. They found gene activity to be reduced in comparison to the adult reference group. The correlation between free BPA and gene expression profiles differed between sexes, suggesting hormone-related effects.
The study sheds light on the somewhat contentious issue of fetal exposure to free BPA, and the potential vulnerability of fetuses to endocrine disruption caused by BPA. An earlier study from Canada (Cao et al. 2012) also measured free and conjugated BPA in human fetal liver samples, however using a smaller sample size (n=28). In this study a slight decrease in conjugated BPA with increasing gestational age was shown. Both studies raise important questions concerning fetal exposure to BPA, and warrant further research.
Nahar, M. S., C. Liao, K. Kannan and D. C. Dolinoy (2012). “Fetal Liver Bisphenol A Concentrations and Biotransformation Gene Expression Reveal Variable Exposure and Altered Capacity for Metabolism in Humans.” Journal of Biochemical and Molecular Toxicology.
Cao, X.-L., J. Zhang, C. G. Goodyer, S. Hayward, G. M. Cooke and I. H. A. Curran (2012). “Bisphenol A in human placental and fetal liver tissues collected from Greater Montreal area (Quebec) during 1998–2008.” Chemosphere 89(5): 505-511.