Protein S is a vitamin K-dependent plasma protein which serves as the cofactor for activated protein C. Protein S circulates in both an active, free form and in an inactive complex with C4b-binding protein. To elucidate the role of protein S in disease states and during oral anticoagulation, we developed a functional assay for protein S that permits evaluation of the distribution of protein S between free and bound forms and permits determination of the specific activity of the free protein S. In liver disease, free protein S antigen is moderately reduced and the free protein S has significantly reduced specific activity. In disseminated intravascular coagulation, reduced protein S activity occurs due to a redistribution of protein S to the inactive bound form. During warfarin anticoagulation, reduction of free protein S antigen and the appearance of forms with abnormal electrophoretic mobility significantly decrease protein S activity. After the initiation of warfarin, the apparent half-life of protein S is 42.5 h. In patients with thromboembolic disease, transient protein S deficiency occurs due to redistribution to the complexed form. Caution should be exercised in diagnosing protein S deficiency in such patients by use of functional assays.
A D'Angelo, S Vigano-D'Angelo, C T Esmon, P C Comp
Usage data is cumulative from April 2023 through April 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 227 | 0 |
98 | 42 | |
Figure | 0 | 3 |
Scanned page | 195 | 24 |
Citation downloads | 15 | 0 |
Totals | 535 | 69 |
Total Views | 604 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.