title: A plasma coagulation assay for an activated protein C-independent anticoagulant activity of protein S.
abstract: To study the physiological importance of the activated protein C (APC)-independent anticoagulant activity of protein S, we developed an assay specific for this activity. The ability of protein S to prolong the clotting time in an APC-independent way was expressed as the ratio of the clotting time in a plasma sample divided by the clotting time in the presence of a polyclonal antibody against human protein S (both after 1:1 dilution in protein S-C4BP deficient plasma). The mean protein S-dependent anticoagulant ratio (PSdAR) was 1.53+/-0.18 in 34 healthy controls, and was significantly lower in 16 heterozygous protein S deficient patients (PSdAR=1.15+/-0.09). In plasmas from patients under oral anticoagulant therapy the mean PSdAR was within the range of the control population (1.50+/-0.18). The mean total protein S antigen level in these plasmas was 58%, suggesting a higher specific APC-independent anticoagulant activity of protein S in these patients than in normals. This functional protein S assay can be used for the laboratory diagnosis of protein S deficiency, and to study the mechanism of the APC-independent anticoagulant activity in plasma.
authors.affiliation: Department of Haematology, University Hospital Utrecht, Institute of Biomembranes, Utrecht University, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: van Wijnen
authors.forename: C
authors.initials: C
authors.lastname: van 't Veer
authors.forename: J C
authors.initials: JC
authors.lastname: Meijers
authors.forename: R M
authors.initials: RM
authors.lastname: Bertina
authors.forename: B N
authors.initials: BN
authors.lastname: Bouma
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology; D001780:Blood Coagulation Tests / Q000379:methods*; D002352:Carrier Proteins / Q000502:physiology; D005260:Female; D006801:Humans; D016167:Integrin alphaXbeta2; D008297:Male; D011486:Protein C / Q000502:physiology; D017293:Protein S / Q000037:antagonists & inhibitors / Q000276:immunology / Q000502:physiology*; D018455:Protein S Deficiency / Q000097:blood / Q000175:diagnosis
chemical_list: D000925:Anticoagulants; D002352:Carrier Proteins; D016167:Integrin alphaXbeta2; D011486:Protein C; D017293:Protein S