Semin Thromb Hemost 2007; 33(1): 041-045
DOI: 10.1055/s-2006-958460
Copyright © 2007 by Thieme Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA.

The Role of Protein C Inhibitor in Human Reproduction

Francisco España1 , Silvia Navarro1 , Pilar Medina1 , Esther Zorio1 , Amparo Estellés1
  • 1Hospital Universitario La Fe, Centro de Investigación, Valencia, Spain
Further Information

Publication History

Publication Date:
23 January 2007 (online)


Protein C inhibitor (PCI) is a heparin-dependent serine protease inhibitor found in human plasma, urine, and other body fluids. In blood plasma, PCI is present at ~0.08 μM and inactivates activated protein C and other coagulation and fibrinolytic enzymes. In seminal plasma, PCI is present at 2.2 to 3.7 μM. The main sources of seminal PCI are the seminal vesicles, where it remains fully active. Following ejaculation, PCI completely looses its activity in approximately 2 hours, when it partially complexes with prostate-specific antigen, two plasminogen activators (urokinase-type and tissue-type plasminogen activators), and tissue kallikrein. PCI is also present in an active form in follicular fluid at ~0.1 μM. Purified functionally active human blood plasma-derived as well as inactive semen-derived PCI inhibited both binding and penetration of zona-free hamster oocytes by human sperm. The binding inhibition by PCI was dose dependent. A concentration of 0.04 μM PCI (~100-fold lower than that present in seminal plasma) inhibited 50% of the binding and penetration ability. Given that capacitated sperm used for in vitro fertilization usually contains more than 0.05 μM of PCI, fertilization rates might be significantly reduced. All of these data suggest that PCI is involved in human reproduction at several steps, including the fertilization process.


Francisco España, Ph.D. 

Hospital Universitario La Fe Centro de Investigación, Av. Campanar

21 46009 Valencia, Spain

Email: [email protected]