Brain-specific protein C activation during carotid artery occlusion in humans

Richard F. Macko, Lois A. Killewich, José A. Fernández, D. Kim Cox, Andras Gruber, John H. Griffin

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Background and Purpose - Activation of plasma protein C (PC) zymogen by thrombin-thrombomodulin at the endothelial surface is an important endogenous antithrombotic mechanism. It is unknown whether activated protein C (APC) is generated in vivo in the cerebrovasculature, because there is only limited thrombomodulin expression in human brain vascular endothelium. Therefore, we tested the hypothesis that carotid occlusion produces brain-specific PC activation. Methods - Blood samples were simultaneously collected from the ipsilateral internal jugular vein and radial artery before and during carotid cross-clamping and on 'de-occlusion' in 8 awake patients undergoing routine carotid endarterectomy. Plasma PC zymogen and circulating APC levels were measured using enzyme immunocapture assay and expressed as percent of pooled plasma controls. Results - Internal jugular vein APC levels increased 28% exclusively during carotid occlusion and then decreased 32% with de-occlusion (F=8.1, P<0.005). PC zymogen increased only 5.9% with occlusion (F=6.3, P<0.02), consistent with hemoconcentration. There were no changes in radial artery PC or APC levels. Conclusions - These findings demonstrate brain- specific protein C activation in humans during carotid occlusion and suggest a protective role for endogenous APC generation during cerebrovascular occlusion.

Original languageEnglish (US)
Pages (from-to)542-545
Number of pages4
Issue number3
StatePublished - Mar 1999
Externally publishedYes


  • Cerebral ischemia
  • Protein C
  • Stroke
  • Thrombomodulin

ASJC Scopus subject areas

  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine
  • Advanced and Specialized Nursing


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