Studies on the apolipoproteins and lipoproteins of cord serum.

Studies on the cord serum lipid transport system were initiated to determine whether there is a correlation between decreased cord serum lipid levels and the absence or diminished level of some or all of the human serum apolipoproteins. Immunologic studies indicated the presence of all the well-characterized apolipoproteins and provided evidence that these apolipoproteins occurred primarily as distinct lipoprotein species with a paucity of association complexes or what others have termed "triglyceride-rich" lipoproteins. Quantitation of the apolipoproteins present in cord serum by electroimmunoassay yielded the following mean levels: A-I = 73O mg/liter; A-II = 410 mg/liter; apolipoprotein B = 280 mg/liter; C-I = 59 mg/liter; C-II = 32 mg/liter; C-III = 65 mg/liter; apolipoprotein D = 37 mg/liter; and apolipoprotein E = 85 mg/liter. Levels of C-I, C-II, and apolipoprotein E approached adult levels (83 to 86% of the adult levels), whereas apolipoproteins B and D were most reduced when compared to the adult concentrations, 29 and 37%, respectively. The three other apolipoproteins were present at approximately one-half the levels found in adults.