Studies of the Metabolism and Distribution of Fibrinogen in Patients with Hemophilia A*

Using autologous (131)I-fibrinogen, we made studies of the metabolism and distribution of fibrinogen in 10 patients with hemophilia A. In two patients simultaneous studies of autologous (131)I-fibrinogen and homologous (125)I-fibrinogen prepared from healthy donors' plasma were carried out. The average value for the plasma volume was 42.1 +/- 8.8 ml/kg; for the plasma fibrinogen concentration, 349 +/- 90 mg/100 ml; for the intravascular fibrinogen, 144 +/- 32 mg/kg; for the interstitial fibrinogen, 30 +/- 11 mg/kg; for the slower half-life of (131)I-fibrinogen, 2.34 +/- 0.17 days; for the transcapillary transfer rate of fibrinogen, 109 +/- 37 mg/kg per day; and for the catabolic and synthetic rates of fibrinogen, 51.7 +/- 13.1 mg/kg per day. Comparison of these results with those of the previous study in healthy male subjects showed that in patients with hemophilia A the catabolic and synthetic rates of fibrinogen are markedly increased, whereas the plasma fibrinogen concentration, intravascular and interstitial fibrinogen, and the transcapillary transfer rate of fibrinogen are not significantly different. The simultaneous studies of autologous (131)I-fibrinogen and normal homologous (125)I-fibrinogen in two subjects revealed that the two preparations behaved very similarly. Based on these findings, we concluded that our present findings are not due to the qualitative difference between the hemophilia A and normal fibrinogens, but that they are due to the difference in the host condition with respect to the fibrinogen metabolism, which is either an increased rate of direct breakdown of fibrinogen or an increased rate of fibrinogen breakdown after fibrin formation, or both.