Urothromboplastin evidence for similarity between urothromboplastin and human brain thromboplastin.

Urothromboplastin (UP) is a lipoprotein similar to Human Brain Thromboplastin (HBrTPL), the specific activity being bound to the presence of the whole complex. UP is found in normal human urine to be macroaggregates, therefore the substance is eluted from the Sepharose 2 B column immediately after the void volume and is found in the bottom of the tube after ultracentrifugation. In polyacrylamidgelelectrophoresis UP does not enter the gel and the UP activity can be eluted from the top of the gel. Natrium-desoxycholate reduces the activity of UP greatly, however after removal of this substance the original activity could be regained. There are similarities between UP and HBrTPL: In the same way as HBrTPL UP acts in the extrinsic pathway of the coagulation system, some evidence for binding of factor VII to UP in the presence of calcium could be found. Anti-apoprotein III antiserum (anti-HBrTPL antiserum) neutralizes UP, depending on the concentration of the antiserum. The same antiserum precipitates with UP using the immunodiffusion method.