THE EFFECT OF CLBAR INHIBITOR UPON HAGEMAN-FACTOR AUTOACTIVATION

Abstract

Using components purified from human plasma, we have examined the effects of .**GRAPHIC**. inhibitor .**GRAPHIC**. INH), the primary inhibitor of activated Hageman Factor (HFa) and Hageman factor fragment (HFf), on Hageman Factor (HF) autoactivation. When Hageman factor was exposed to a negatively charged surface, provided by either a glass cuvette or dextran sulfate, the addition of .**GRAPHIC**. INH gave a dose-dependent inhibition of the activity observed. The ability of .**GRAPHIC**. INH to decrease the maximal enzymatic activity generated was markedly temperature dependent with inhibition increasing as the temperature was raised from 4.degree. C to 37.degree. C. Although the rates of both autoactivation and inhibition were decreased at lower temperatures (4.degree. C), the latter rate was more sensitive to temperature modulation. When HF (final concentration 1 .mu.mol/L) was incubated with .**GRAPHIC**. INH (0.54, 1.07, and 2.14 .mu.mol/L) in the absence of an initiating surface, no increases in enzymatic activity were observed for up to 48 hours regardless of the .**GRAPHIC**. INH concentration. However, SDS polyacrylamide gel electrophoresis of the incubation mixture revealed that HF autodigestion had occurred by 48 hours despite the presence of .**GRAPHIC**. INH. In addition, the appearance of a new band suggested that a complex had been formed between the inhibitor and activated HF. Our findings indicate that .**GRAPHIC**. INH does not prevent HF autoactivation but rather inactivates the products of HF autodigestion.