A method for the differential determination of plasma antithrombins

SYNOPSIS A method for the differential determination of plasma antithrombins, antithrombin III and U macroglobulin, is described. The method is based on the selective inactivation of plasma (x2 macroglobulin by treatment with 01 M methylamine for 10 minutes at 37°C and on the observa-tion that antithrombin III and a2 macroglobulin inhibited in defibrinated plasma low concentrations of thrombin without mutual interference and according to pseudo-first order reaction. In healthy subjects antithrombin III was shown to account for about 70 % of the total antithrombin activity. But in patients with liver cirrhosis, where low levels of total antithrombin activity were observed, the relative contribution of antithrombin III was found to be noticeably lower. Three different thrombin inhibitors have been puri-fied from human plasma, namely, an Ox2 globulin called antithrombin III (Abildgaard, 1967; Heimburger, 1967), the 02 macroglobulin (02M) (Lanchantin et al, 1966; Steinbuch et al, 1968), and the al1 antitrypsin (Rimon et al, 1966; Gans and Tan, 1967)