Separation and Characterization of Cord Serum Lipoproteins

Abstract

Summary: Blood was collected from the umbilical cords of infants with a 1-min Apgar score of 9 or 10. Total cord serum lipoproteins were isolated by ultracentrifugation, at a density of 1.220 g/ml. The isolated serum lipoproteins were then separated by gel filtration chromatography on 6% agarose. The overall recovery of the separated lipoprotein cholesterol was 90% or greater. In cord serum, four lipoprotein peaks were found, whereas three peaks were present in adult lipoproteins. The major lipoproteins of cord serum correspond to low density lipoprotein (LDL) and high density lipoprotein (HDL). Very low density lipoproteins (VLDL) were heterogeneous in cord serum. After gel filtration chromatography, the distribution of cord serum cholesterol is about 5% in peak 1, 10% in peak 2, 40% in peak 3 (LDL), and 45% in peak 4 (HDL). An additional difference between the lipoproteins isolated from cord serum and those from adult serum was the slower electrophoretic mobility of cord serum VLDL in agarose gel.

Speculation: The fetus, during the later stages of pregnancy, accumulates fat at an accelerating rate. Triglycerides, synthesized by the liver, are secreted as VLDL and transported to adipose tissue for degradation, probably by lipoprotein lipase.

The heterogeneity of cord blood VLDL and the presence of a significant amount of an intermediate lipoprotein fraction (designated peak 2) may be related to a partial metabolic block in the conversion of VLDL lipoproteins to smaller lipoproteins such as LDL.

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