Vitamin D metabolism in human pregnancy. Concentrations of free and sulphated 25-hydroxyvitamin D3 in maternal and fetal plasma at term.
The concentrations of free and sulphated 25-hydroxyvitamin D3 in 20 paired maternal-cord plasma samples obtained at delivery have been determined. The compounds were isolated by liquid-solid extraction at elevated temperature, and the sulphate was purified by anion exchange chromatography prior to hydrolysis and analysis by high-performance liquid chromatography. The study shows that unconjugated 25-hydroxyvitamin D3 is predominant in maternal plasma (mean 20 ng/ml) whereas the sulphate is the major form of vitamin D3 in fetal circulation (mean 21 ng/ml plasma). The total concentration of the two compounds in cord plasma (mean 35 ng/ml) was significantly higher than that in maternal plasma (mean 30 ng/ml). Positive correlations were obtained between maternal and cord plasma levels of free 25-hydroxyvitamin D3, between maternal and cord plasma levels of sulphated 25-hydroxyvitamin D3 and between plasma levels of the maternal free compound and the fetal sulphate. There was also a relationship between the levels of free and sulphated 25-hydroxyvitamin D3 in cord plasma. The results suggest that sulphation may be a physiologically important reaction for deactivating and/or trapping secosteroids in the fetus.
Axelson
M
M
Department of Clinical Chemistry, Karolinska Hospital, Stockholm, Sweden.
Christensen
N J
NJ
D000328:Adult; D002112:Calcifediol / Q000097:blood*; D002852:Chromatography, Ion Exchange; D005260:Female; D005312:Fetal Blood / Q000032:analysis*; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy / Q000097:blood*; D013431:Sulfates; D013696:Temperature; D014807:Vitamin D / Q000097:blood*
D013431:Sulfates; D014807:Vitamin D; D002112:Calcifediol