title: Rapid amidolytic assay of protein C in whole plasma using an activator from the venom of Agkistrodon contortrix.
abstract: A rapid assay for protein C activity in whole plasma using a protein C activator from the venom of Agkistrodon contortrix is described. Plasma samples are incubated with venom activator in the presence and absence of anti-protein C antibody for 8 minutes at 37 degrees C in microtiter plate wells, followed by addition of a chromogenic substrate for activated protein C and measurement of the absorbance at 405 nm after 10-20 minutes incubation at 37 degrees C. The difference in absorbance between plasma assayed in the presence and absence of anti-protein C antibody is used to calculate the protein C activity by reference to a dilution curve of normal plasma. With this assay, mean protein C activity in 33 normal subjects was 87%. Thirty-eight patients receiving warfarin had a mean protein C of 34%. Twenty-four patients with disseminated intravascular coagulation had a mean protein C of 24%. The venom activator appears to preferentially activate gamma-carboxylated protein C, indicating specificity for the physiologically active form of the molecule.
mesh_terms: D000577:Amides / Q000378:metabolism; D001777:Blood Coagulation / Q000187:drug effects; D003435:Crotalid Venoms / Q000494:pharmacology; D004211:Disseminated Intravascular Coagulation / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008722:Methods; D011486:Protein C / Q000037:antagonists & inhibitors / Q000097:blood*; D013927:Thrombosis / Q000097:blood / Q000188:drug therapy; D013997:Time Factors; D014859:Warfarin / Q000627:therapeutic use
chemical_list: C031442:Agkistrodon venoms; D000577:Amides; D003435:Crotalid Venoms; D011486:Protein C; D014859:Warfarin