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Cobalamin binding proteins in the human fetus.
M Hansen1, C K Høgdall, N Kryger-Baggesen
1Department of Medicine and Haematology, Gentofte Hospital, University of Copenhagen, Denmark.
Summary
Fetal development includes synthesizing cobalamin-binding proteins by 16-19 weeks. Fetal cerebrospinal fluid and amniotic fluid contain adult-like binding proteins, but fetal serum shows lower cobalamin-binding capacity than adults.
Area of Science:
- Biochemistry
- Fetal Development
- Nutritional Science
Background:
- Cobalamin (Vitamin B12) is essential for fetal development.
- Cobalamin binding proteins, including haptocorrin, intrinsic factor, and transcobalamin, facilitate vitamin B12 transport and availability.
- Understanding the developmental profile of these proteins is crucial for assessing fetal nutritional status.
Purpose of the Study:
- To characterize cobalamin binding proteins and their unsaturated binding capacity in fetal biological fluids.
- To compare fetal levels with adult reference values.
- To investigate the presence and characteristics of these proteins in amniotic fluid.
Main Methods:
- Analysis of cerebrospinal fluid (CSF), serum, and amniotic fluid from fetuses and newborns.
- Characterization of cobalamin binding proteins using size exclusion chromatography and isoelectric focusing.
- Quantification of unsaturated cobalamin-binding capacity (UCC).
Main Results:
- Fetal synthesis of cobalamin binding proteins begins by 16-19 weeks of gestation.
- Transcobalamin in fetal CSF exhibited identical characteristics to adult transcobalamin.
- Fetal CSF and amniotic fluid contained adult-like haptocorrin, intrinsic factor, and transcobalamin.
- Unsaturated cobalamin-binding capacity in fetal CSF was comparable to adult levels.
- Serum unsaturated cobalamin-binding capacity was lower in fetuses compared to adults, but significantly higher in term umbilical cord serum than in fetal CSF.
- Umbilical cord serum UCC was approximately two-thirds of maternal serum UCC.
Conclusions:
- Cobalamin binding proteins are present and mature in fetal CSF and amniotic fluid early in gestation.
- While fetal CSF shows adult-like binding capacity, fetal serum exhibits lower levels, suggesting developmental regulation.
- Term umbilical cord serum demonstrates a distinct and higher unsaturated cobalamin-binding capacity compared to fetal serum, approaching maternal levels.