An amidolytic assay system with tissue thromboplastin (Tpl), purified coagulation
factors VII and X, and the chromogenic substrate S-2222 was developed. Antithrombin
III (AT) accounts for about one third of the total inhibition exerted by normal plasma
in this test system. This effect of AT was prevented by adding purified AT blocking
antibodies. Normal plasma and serum showed approximately similar inhibitory effects.
The inhibition was probably directed against activated factor VII (F VIIa). Gel filtration
of adsorbed normal plasma on Ultrogel AcA 34 showed three inhibitory peaks which were
different from AT.
Keywords
Key words Factor VII - Coagulation inhibitors - Chromogenic substrates