Effect of Air Currents on Plasma Prothrombin. ∗

Tocantins 1 recently reported that plasma exposed to air currents showed a rapid diminution of prothrombin activity and that addition of CO₂ restored this loss. In view of the importance that these results have in the quantitative determination of prothrombin, and in the possible solution of the problem of preventing the spontaneous loss of this clotting factor in stored blood, it seemed important that these experiments be repeated.

Four cc of oxalated plasma were put in a pyrex test tube (25×100 mm) fitted with a 2-hole rubber stopper through which were inserted 2 glass tubes. One of the tubes nearly reached the surface of the plasma. The test tube was tilted to expose a maximum area of plasma surface, and a stream of air (first passed through a dilute solution of sodium hydroxide to remove CO₂) was blown over the plasma, kept at 38°C. The “prothrombin time” was determined by the author's method 2 and the CO₂ content by Van Slyke's original volumetric method. The loss of volume by evaporation was restored by adding distilled water.

The results indicate that the prothrombin of dog and rabbit plasma is not demonstrably altered by one hour aeration even though considerable CO₂ is lost. Human plasma aerated at room temperature likewise does not lose any significant amount of prothrombin activity in one hour. At 38°C, however, a definite loss of prothrombin occurs, which the addition of CO₂ does not restore. It appears, therefore, that the decrease of prothrombin is due to direct oxidative destruction or to the formation of an oxidation product in plasma which inactivates prothrombin, rather than to the loss of CO₂ from the plasma.