On the rôle played by antagonistic ions in the process of blood coagulation

Abstract

Citrated plasma prepared by admixing three parts of blood with one of 2.38 per cent. sodium citrate and centrifuging, coagulates almost immediately when admixed with an amount of CaCl₂ chemically equivalent to 4/10 to 1/2 of the citrate present. If additional citrate is added to the plasma, it is necessary to proportionately increase the amount of calcium added to induce coagulation. With thrombin, however, coagulation of plasma takes an entirely different course, the velocity of coagulation is considerably slower, but is apparently entirely uninfluenced by an excess of citrate. It may be concluded, therefore, that calcium induces coagulation by liberating thrombin from the blood platelets or other cells present in suspension in the plasma. To throw further light on this point, equal volumes of the same citrated plasma were precipitated by means of a considerable excess of a mixture of acetone and ether (an agent which has proved of considerable value in the preparation of thrombin) an excess of calcium chloride being added in one case immediately before and in the second case immediately after precipitation. The mixtures containing acetone ether were evaporated in vacuo at room temperature, the residues taken up with water and added to further amounts of citrated plasma to which an excess of citrate had previously been added. In the first case in which the calcium chloride was added before precipitation, coagulation took place rapidly, indicating the presence of free thrombin. In the second case in which the calcium was added after precipitation, no coagulation took place on addition of plasma, from which it must be concluded that by the process of precipitation the cells containing the thrombin have been rendered resistant to the action of calcium.