AN INTERMEDIARY CALCIUM COMPLEX IN BLOOD COAGULATION

Abstract

In a series of controlled exps., plasma thrombin (prothrombincephalin-Ca mixture) (a), "fresh" (few minutes); (b), "ripe" (several hrs.), and (c), electrodialyzed (Ca-free), was subjected to oxala-tion and citration before testing clotting activity on prothrombin-free fibrinogen. The decalcifying anticoagulants show 3 phenomena: prevention of thrombin formation by depressing ionization of the Ca salts essential for activation; progressive inactivation of "fresh" thrombin; and a characteristic immediate effect (varying with concn.) which is the sole action seen in tests on "ripe" and electro-dialyzed thrombin. The evidence adduced points to a Ca-containing intermediary complex in the formation of thrombin. The activity of the "ripe" coagulant, however, is essentially independent of Ca.