Maternal - Fetal Interaction: An Insight through the Stable Isotope Fractionation Prism

Aims: To compare carbon and nitrogen isotopic composition of maternal and fetal organs.
Study Design: Cross-sectional study.
Place and Duration of Study: Biology Department of Lomonosov Moscow State University; Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences; 2008 – 2011.
Methodology: Mass spectrometric measurements of carbon and nitrogen isotopic ratios of corresponding maternal and fetal organs of gravid mice fed a monotonous diet.
Results: Both the maternal and fetal organs (kidney, muscles, liver, myocardium, brain) of mice at the last term of gestation are enriched in 13C and 15N relative to food consumed. Isotopic composition of organs strongly depends on the number of bearing fetuses. The increase of fetuses’ number results in coordinated 13C depletion and 15N enrichment in both the maternal and fetal organs.
Conclusion: The alteration of the δ13C and δ15N values reflects solely the metabolic restructuring during a pregnancy, since mice were fed the monotonous diet prior to conception and during gestation. Isotopic alterations develop as a reaction to the nutritional stress of the maternal organism under the trophic demands of fetuses. The protein replenishment is the most probable cause of isotope ratio changes. Under the controlled experimental condition the stable Isotope composition of biogenic elements can be used as integral indicators of metabolic efforts of the particular organismic structures. The predictive role of such integral indicators consists at least in limitation of possible biochemical conversions underlying the metabolism change.