Abstract
Recent investigations, 1 , 2 indicate that satisfactory methods for the quantitative determination of prothrombin have been developed.
These methods are dependent on the original suggestion of Quick, Stanley-Brown and Bancroft 3 that the coagulation time of oxalated plasma, when mixed with an excess of thromboplastin and then recalcified is a direct measure of the prothrombin content of the plasma. Subsequent studies have led some investigators to conclude that the defect in the coagulation of the blood in certain cases of jaundice is due to a deficiency of prothrombin.
The methods followed in the present studies were essentially the same as those described by Quick. 1 , 4 The prothrombin time was determined on 0.1 cc portions of oxalated plasma in clean, dry 100 × 13 mm test tubes in a water bath at 37.5°C. An excess of thromboplastin was supplied by the addition of 0.1 cc of a freshly prepared saline suspension of an acetone extract of rabbit brain. Theoretically the thromboplastic preparation served to convert all of the prothrombin to thrombin. Upon recalcification with 0.1 cc of a 0.025 M calcium chloride solution, which was considered to be the optimal amount of calcium, 1 it was observed that the results were extremely variable. Furthermore, it was usually impossible to obtain a fibrin clot in normal plasma in from 12 to 13 seconds 1 unless the concentration of calcium was altered.
Eleven solutions of calcium chloride varying in concentration from 0.1 M to 0.000625 M were prepared. The effect of each of these solutions as a recalcifying agent in the determination of prothrombin was studied on plasma obtained from 20 normal individuals. In each instance the results were entirely similar. The observations in one typical case are shown in Table I.
Get full access to this article
View all access options for this article.