STUDIES ON BLOOD COAGULATION I lL ON Tm~ CONSTANCY OF THE HYDROGEN ION CONCENTRATION DURING THE COAGULATION 0]~ FIBRINOGEN BY THROM-BIN BY HARRY EAGLE* A~D

Kugelmass and Stuber and Lang have reported that the coagulation of blood or solutions of fibrinogen is accompanied by an increased alkalinity of the free fluid, which the former definitely ascribes to an absorption of hydrogen ions by the clot. Hirsch, however, reports an increased acidity, and suggests that it is the actual cause of coagulation; and Hekma in claiming that fibrinogen is the alkaline hydrosol of fibrin, implies that he believes its coagulation to be due to an acidification of shed blood. Finally, Havard and Kerridge report that the time-pH curve of shed blood is unaffected by coagulation. Clearly, the matter requires reinvestigation. If it could be proved that the transformation of fibrinogen to fibrin is invariably accompanied by a change in the hydrogen ion concentration of the free fluid, such a change would offer a valuable clue to the essential difference between the two proteins. With this in mind, thrombin was added to solutions of horse and rabbit fibrlnogen, and the pH followed potentiometrically. Fibrinogen and thrombin were prepared as described in a preceding paper (Eagle). Error due to loss of CO~ was minimized by using a fibrinogen solution in equilibrium with air. The prothrombin used in preparing the thrombin was adjusted to approximately pH 6.5 prior to the addition of CaC12, in several experiments using dilute NaOH