Abstract
Free fatty acids (FFA) are strong bilirubin displacers from Albumin (A) at FFA:A ratio >3:1. A model of bilirubin displacement using FFA:A ratio to predict free bilirubin was tested in 21 sera from 14 newborns (8 sick, 6 well). Concentration of FFA was 0.64 ± 0.40 mEq/1, A 0.41 ± 0.09 mEq/1, and FFA:A was 1.6 ± 1.0 (Mean ± S.D.); FFA:A was <3:1 in 20 of 21 sera, regardless of clinical condition. Free bilirubin (peroxidase assay, pH 7.4, serum dilution 1:40, 25°C) correlated with bilirubin: albumin molar ratio (r = 0.845, p <0.01), but was higher than predicted from the FFA:A ratios, even without a history of displacing drugs, suggesting the presence of other displacers. To reduce the effect of dilution in the peroxidase assay and restore the free serum concentrations of weak displacers, protein-free ultrafiltrates of 10 sera were made by centrifugation. Incubation of the 10 sera with their ultrafiltrates gave a 1.5 to 4 fold further displacement of bilirubin, proportional to the amount of ultrafiltrate added in the test. The data suggest that neonatal sera contain bilirubin displacers other than FFA or drugs whose effect on free bilirubin is reduced by dilution during the assay. Use of ultrafiltrates allows re-equilibration of serum albumin with weak displacers and a more accurate assessment of their potential clinical significance.
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Cashore, W., Brodersen, R. & Oh, W. 234 EFFECT OF FREE FATTY ACIDS AND OF SERUM ULTRAFILTRATES ON BILIRUBIN DISPLACEMENT IN NEONATAL SERUM. Pediatr Res 12 (Suppl 4), 402 (1978). https://doi.org/10.1203/00006450-197804001-00239
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DOI: https://doi.org/10.1203/00006450-197804001-00239