title: Antithrombin III, the major modulator of intravascular coagulation, is synthesized by human endothelial cells.
abstract: Human endothelial cells in culture is shown to synthesize antithrombin III (At-III). The endothelial cell At-III (EC-At-III) consists of a small fraction similar to plasma At-III and a larger fraction with decreased heparin-binding as tested by crossed immunoelectrophoresis. However, both the anti-Xa and thrombin-neutralizing activities of the EC-At-III were rapid and active even in the absence of added heparin. It is concluded that the major portion was probably bound to endogenous heparin-like substance, thus accounting for its decreased exogenous heparin binding. The presence of At-III and other antithrombotic factors in the vascular endothelium offer protection against thrombosis and possibly atherosclerosis.
mesh_terms: D000990:Antithrombin III / Q000096:biosynthesis* / Q000494:pharmacology; D001345:Autoradiography; D001808:Blood Vessels / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D004727:Endothelium / Q000378:metabolism; D005170:Factor X / Q000037:antagonists & inhibitors; D015951:Factor Xa; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D009500:Neutralization Tests; D013917:Thrombin / Q000037:antagonists & inhibitors
chemical_list: D000990:Antithrombin III; D005170:Factor X; D006493:Heparin; D013917:Thrombin; D015951:Factor Xa