Thermolability of the Tissue Extract Factor in Extract Activation

Abstract

The writer has found that the addition of one volume of rabbit plasma to 60-100 volumes of chick embryo extract greatly increases the coagulative power of the extract 1 ; that the increase of power is due to the appearance of a body which shows the same sensitivity to heparin as thrombin 2 ; that the body reacts like thrombin in the presence and absence of ionic calcium 3 ; that thermolability studies on the plasma factor indicate that this factor is prothrombin 4 . Mills and Matthews 5 found that mixtures of rabbit serum and lung extract show a temporary increase in coagulative power. Burns, Scharles, and Aitkin 6 have recently restudied the clotting power of extracts and sera from various sources. The papers cited above and some unpublished work made it reasonable to suppose that the cephalin in tissue extracts might be the factor involved in activation.

It is generally accepted that the only coagulation factor surviving boiling is cephalin. Mills 7 uses this as a method of distinguishing between tissue fibrinogen and cephalin in his study of blood platelets.

In this study chick embryo extract is made by extracting a 10 day embryo with Ringer solution. Coagulative power is tested by determining the shortening of the clotting time of a recalcified citrate rabbit plasma. Clotting time is done in 10 mm. tubes. In each test 2 drops of citrate plasma plus optimal amount 1% CaCl₂ plus 1 drop of the coagulant plus sufficient .9% NaCl to make a total of 10 drops are used. In this way the concentration of fibrinogen is kept constant. Activation is carried out by adding 1 part of citrate plasma to 20 parts chick extract. Pipettes are calibrated to drop 0.05 cc. Determinations have been made between 30° C. and boiling at intervals of 10°.