Thromb Haemost 1987; 58(04): 0998-1004
DOI: 10.1055/s-0038-1646044
Original Article
Schattauer GmbH Stuttgart

Immunoradiometric Assay for the Calcium-Stabilized Conformation of Human Protein S

S R Poort
The Hemostasis and Thrombosis Research Unit, Department of Hematology, Leiden University Hospital, Leiden, The Netherlands
,
P P Deutz-Terlouw
The Hemostasis and Thrombosis Research Unit, Department of Hematology, Leiden University Hospital, Leiden, The Netherlands
,
A van Wijngaarden
The Hemostasis and Thrombosis Research Unit, Department of Hematology, Leiden University Hospital, Leiden, The Netherlands
,
R M Bertina
The Hemostasis and Thrombosis Research Unit, Department of Hematology, Leiden University Hospital, Leiden, The Netherlands
› Author Affiliations
Further Information

Publication History

Received 20 March 1987

Accepted after revision 29 July 1987

Publication Date:
29 June 2018 (online)

Preview

Summary

Rabbit polyclonal anti-protein S serum was fractionated with immobilized human protein S to establish solid-phase immunoradiometric assays recognizing Ca(II)-dependent and NonCa(II)-dependent epitopes of human protein S. The two assays were specific for PS:Ca(II)Ag and PS:NonCa(II)Ag and highly sensitive with a lower limit of detection of about 2.5 ng/ml.

PS:Ca(II)Ag and PS:NonCa(II)Ag levels were measured in immunopurified protein S, thrombin-modified protein S and chy-motrypsin-cleaved protein S. Only in chymotrypsin-cleaved protein S an important discrepancy between the two antigen levels was observed.

Ranges for the concentration of PS:Ca(II)Ag and PS:NonCa(II)Ag and their ratio were established in plasma of healthy individuals (0.92 ± 0.13 U/ml, 0.98 ± 0.21 U/ml, 0.96 ± 0.17, respectively). In a group of patients using oral anticoagulant therapy the ratio PS:Ca(II) Ag/PS : NonCa(II)Ag decreased at increasing intensity of anticoagulation suggesting the presence of sub- and noncarboxylated protein S molecules.

In plasma of patients with a hereditary type I protein S deficiency PS:Ca(II)Ag and PS:NonCa(II) Ag were reduced to the same extent: mean ratio 1.02 ± 0.12 in the group not on oral anticoagulant treatment and 0.94 ± 0.10 in the group on oral anticoagulant therapy. Analysis of patients with a history of unexplained thrombo-embolic disease did not reveal individual patients with a PS:Ca(II)Ag/PS:NonCa(II)Ag ratio below the lower limit of the normal range (mean ratio 1.05 ± 0.17), suggesting that the frequency of genetic protein S variants with defects in the Ca(II)-stabilized conformation is very low.