Action of Disodium Ethylenediamine Tetracetate on Blood Coagulation : Evidence of the Development of Heparinoid Activity during Incubation or Aeration of Plasma

A. The action of EDTA on the coagulation mechanism was studied. EDTA was found:

1. To exert no direct effect on prothrombin or thrombin.

2. To have an inhibitory action on labile factor.

3. To increase the speed of conversion of prothrombinogen to prothrombin.

B. The effect of incubation or aeration of plasma on thrombin time was studied. It was found that aeration or incubation increases the thrombin time of plasma. The following observations lead one to attribute this prolongation to a heparinoid activity:

1. The property of incubated plasma to prolong the thrombin time of fresh plasma when added to it.

2. The ability of protamine to shorten the thrombin time of incubated or aerated plasma.

3. The sensitivity of the thrombin time of incubated or aerated plasma to pH changes and calcium concentration.

C. The incidental observation was made that cooling reverses the prolonged thrombin time produced by incubation.