Hypoxia induces procoagulant activity in cultured human venous endothelium

Although it normally presents a nonthrombogenic surface, endothelium is capable of procoagulant activity and suppression of native anticoagulant properties. We theorized that hypoxia could shift normal endothelium into a procoagulant state and tested this hypothesis in cultured human umbilical venous endothelial cells. Human umbilical venous endothelial cells were obtained from fresh umbilical cords. Passage two cells were placed in control (PO2 greater than 120 mm Hg) or hypoxic (PO2 less than 60 mm Hg) media and incubated in control or hypoxic environments for 24 hours. In additional experiments, cells were reoxygenated for 4 or 48 hours after the initial hypoxic period. Cells were then assayed for procoagulant activity expressed as thromboplastin unit equivalents per 100,000 cells based on a thromboplastin standard curve. Results are expressed as percent increase in thromboplastin unit equivalents/100,000 cells +/- standard error versus control. Statistical significance was assessed by paired t test with p less than 0.05 considered significant. More than 95% of cells in all experimental and control preparations were viable after completion of the protocols. No morphologic variation was noted among the control and hypoxic groups. For cells rendered hypoxic without reoxygenation, the mean increase in procoagulant activity for the group (n = 4) versus control was 77% +/- 13% (p = 0.01). In the hypoxia and 4-hour reoxygenation group (n = 4), the mean increase in procoagulant activity was 141% +/- 43% (p less than 0.05). In cells reoxygenated for 48 hours after hypoxia (n = 8), the mean increase in procoagulant activity was 198% +/- 34% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)