Changes in polypeptide-specific factor VIII antigen levels during whole blood clotting.
The time-course of factor VIII (FVIII) proteolysis during whole blood coagulation was monitored using polypeptide-specific enzyme-linked immunosorbent assays (ELISAs) developed with monoclonal antibodies to FVIII. Such assays of whole blood from normal subjects revealed that, within 30 min after coagulation had started, levels of the amino-terminal region of FVIII light chain and in the middle region of FVIII heavy chain had decreased to baseline in parallel with factor VIII procoagulant activity, but that levels of the 70 kDa thrombin digest decreased more slowly, with 75 U/dl of FVIII antigen (FVIII:Ag) remaining even after 2 h. Similar analysis of the blood of a patient with congenital hypoprothrombinemia indicated a lag phase of 20 min before proteolysis started. No significant change was observed until 1 h after calcium chloride was added to prothrombin-depleted plasma. On the other hand, in the presence of tissue thromboplastin, levels of FVIII:Ag in all ELISAs decreased rapidly. These results indicate a requirement for thrombin generation in the proteolysis of FVIII during the process of whole blood clotting.
Tanaka
I
I
Department of Pediatrics, Nara Medical College, Japan.
Yoshioka
A
A
Shima
M
M
Fujiwara
T
T
Terada
S
S
Nakai
H
H
Sawamoto
Y
Y
Kamisue
S
S
Fukui
H
H
D001777:Blood Coagulation / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D005169:Factor VIII / Q000276:immunology*; D006801:Humans; D010455:Peptides / Q000276:immunology*
D000939:Epitopes; D010455:Peptides; D005169:Factor VIII