A new technique for studying the relationship between maternal diabetes and the sialic acid content of fetal pulmonary surfactant.
By adapting a standard method for precipitation of high-density lipoprotein cholesterol with phosphotungstic acid (PTA) and Mg2+, fetal pulmonary surfactant can be rapidly isolated from human amniotic fluid, 97% of the total disaturated phosphatidylcholine being precipitated from the sample. The lecithin/sphingomyelin ratio for 17 separate specimens correlated reasonably well (r = 0.76) with the concentration of disaturated phosphatidylcholine in the PTA precipitate. Using thiobarbituric acid as the chromophore, I measured sialic acid in the PTA precipitate after overnight treatment with neuraminidase. The sialic acid/protein ratio for the PTA precipitate was identical to that for the surfactant, as isolated by ultracentrifugation. The concentrations of insulin and C-peptide were significantly greater in specimens of amniotic fluid from mothers with diabetes than from non-diabetic mothers (p less than 0.001). When the specimens were segregated according to a C-peptide cutoff value of 4 micrograms/L, there was a small, significant decrease in PTA-precipitated concentrations of sialic acid in the samples with C-peptide greater than 4 micrograms/L. The results suggest a possible mechanism for the increased incidence of respiratory distress among infants born to diabetic mothers.
D000653:Amniotic Fluid / Q000032:analysis*; D001059:Apoproteins / Q000032:analysis; D002096:C-Peptide / Q000032:analysis; D055598:Chemical Phenomena; D011232:Chemical Precipitation; D002621:Chemistry; D005260:Female; D005333:Fetus / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000032:analysis; D010713:Phosphatidylcholines / Q000032:analysis; D010772:Phosphotungstic Acid; D010865:Pilot Projects; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011254:Pregnancy in Diabetics / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000032:analysis*; D012794:Sialic Acids / Q000032:analysis*; D013109:Sphingomyelins / Q000032:analysis
D001059:Apoproteins; D002096:C-Peptide; D007328:Insulin; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D012794:Sialic Acids; D013109:Sphingomyelins; D010772:Phosphotungstic Acid