Received on July 21, 2005
Accepted on November 23, 2005

General Clinical Chemistry

The Cobalamin Binding Proteins Transcobalamin and Haptocorrin in Maternal and Cord Blood Sera at Birth

¹ Department of Clinical Chemistry, Faculty of Medicine, University Hospital of Saarland, Homburg/Saar, Germany
² Department of Clinical Biochemistry, NBG, AS, Aarhus University Hospital, Denmark
³ Department of Obstetrics and Gynaecology, Faculty of Medicine, University Hospital of Saarland, Homburg/Saar, Germany

Background: Two proteins carry vitamin B₁₂ in plasma. Transcobalamin (TC) carries 25% of total plasma vitamin B₁₂ and is 6% to 20% saturated with cobalamin. Haptocorrin (HC) binds 80% of total cobalamin and is largely saturated with cobalamin.

Methods: We investigated the distribution and the relationship between concentrations of cobalamin, total and holo forms of TC, and HC in blood samples from pregnant women just before delivery (n = 92) and in cord blood samples from their newborn babies. Furthermore, we investigated the relationship between these proteins and concentrations of methylmalonic acid (MMA), the functional marker of vitamin B₁₂ status.

Results: Concentrations of total serum cobalamin, total HC, holoHC, and percentage of HC saturation were higher in cord blood than in the maternal blood (mean cobalamin, 268 vs 188 pmol/L; total HC; 648 vs 538 pmol/L; holoHC, 441 vs 237 pmol/L; HC-saturation, 70% vs 47%). Moreover, total TC was low in cord blood while both holoTC and TC saturation were higher in cord blood than in the maternal blood (mean total TC, 654 vs 1002 pmol/L; holoTC; 118 vs 53 pmol/L; TC-saturation, 19.8% vs 5.4%). Higher maternal serum cobalamin was associated with higher cord blood holoTC and TC-saturation (P <0.05). Gestational age was also a significant determinant of baby total TC, TC-saturation, total HC, and holoHC.

Conclusions: The close correlation between the amounts of holoTC present in cord blood and in maternal serum supports the importance of the maternal cobalamin status ensuring a sufficient supply to the baby.