Reevaluation of some properties of fibrinogen, purified from cord blood of normal newborns

Some properties of fibrinogens, obtained from normal adult and cord plasma, were compared. Fibrinogen preparations were made under conditions which minimize proteolytic breakdown in vitro. It was not possible to demonstrate any significant differences between both purified fibrinogens as to the effects of pH and ionic strength on its clotting properties, the Km for thrombin, SDS [sodium dodecyl sulfate] polylacrylamide gel electrophoresis behavior or carbohydrate content. However, the content of cord fibrinogen was 3-4 times higher than that of adult fibrinogen. The accelerating effect of Ca on the thrombin clotting time was more pronounced for newborn cord plasma and for purified cord fibrinogen preparations as compared with adult fibrinogen. This might be explained by the higher P content of the cord fibrinogen molecule. The thrombin clotting time of both purified adult and cord fibrinogen was markedly prolonged, when increasing amounts of fibrinogen degradation product fragment X were added to the fibrinogen solutions under conditions with high pH or high ionic strength. At high pH the effect of adding fragment X was more pronounced in cord fibrinogen preparations. Therefore, mixtures of purified fibrinogen and fragment X have several properties in common with fetal fibrinogen. Some of the properties that were attributed in the literature to a distinct fetal fibrinogen apparently can be caused by the presence of fragment X in the cord fibrinogen preparations.