Thrombomodulin activity in commercial thromboplastin preparations.
Recently, it was reported that endothelial cells contain a membrane protein which serves as a cofactor for the activation of protein C by thrombin (thrombomodulin). Because many commercial thromboplastins are prepared from vessel-rich tissues/organs (lung, brain, placenta), it was hypothesized that some preparations may contain significant amounts of thrombomodulin; theoretically, thrombomodulin contaminations may enhance the prothrombin time. Among 8 different commercial thromboplastins tested two thromboplastins were found to contain significant amounts of thrombomodulin activity: Simplastin (64 U/ml) and Ortho (12.8 U/ml). However, we were unable to demonstrate that the presence of the thrombomodulin activity in these thromboplastins could affect the prothrombin time either by delaying fibrin formation (formation of thrombin-thrombomodulin complexes) or by inhibiting activated factor V (formation of activated protein C).
D005340:Fibrinogen / Q000378:metabolism; D006023:Glycoproteins / Q000097:blood; D006801:Humans; D011486:Protein C; D011517:Prothrombin Time; D011956:Receptors, Cell Surface / Q000302:isolation & purification*; D018179:Receptors, Thrombin; D013917:Thrombin / Q000378:metabolism; D013925:Thromboplastin / Q000302:isolation & purification*
D006023:Glycoproteins; D011486:Protein C; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D005340:Fibrinogen; D013925:Thromboplastin; D013917:Thrombin