Correction of the Delayed Fibrin Aggregation of Fetal Fibrinogen by Partial Removal of Sialic Acid

Abstract

Human umbilical oord fibrinogen characteristically displays delayed fibrin aggregation under conditions of relatively high ionic strength. This delay is greater in fibrinogen obtained from premature (p) (24–35 weeks gestation) infants, as compared with that from full term (FT) infants. We compared the sialic acid content of (fraction I-2) fetal (P and FT) with adult (A) fibrinogen, obtained from pooled plasma. The mean sialic acid μg/100mg protein) values were: P, 818 (±135 SD, range 621–1030); FT, 720 (±212, range 505–1280); A, 626 (±110, range 487-806). One P fibrinogen preparation (thrombin time 22.6 seconds) was partially desialated (resulting sialic acid value 490) by incubation with Vibrio cholera neuraminidase, dialyzed , and precipitated with ethanol to remove free sialic acid. The thrombin time of the resulting preparation was 15.4 (range 15.2–15.8), compared to 16.1 (range 15.5–16.4) for untreated A fibrinogen. The results suggest that the delayed fibrin aggregation of fetal fibrinogen is attributable to its relatively high sialic acid content. Moreover, the intermediate sialic acid (and thrombin time) values of FT (as compared to those of p) fibrinogen intimate the presence of a mixture of adult and fetal fibrinogen in full term cord blood.