THE ASSOCIATION OF FACTOR VIIA, FACTOR XIIA AND BETA(2)-GLYCOPROTEIN-1 WITH TRIGLYCERIDE-RICH LIPOPROTEINS IN NORMOLIPIDEMIC SUBJECTS

The activation of factors XII (FXII) and VII (FVII) has been shown to occur on the surface of lipoproteins in the presence of lipoprotein li pase and may be modulated by beta(2)glycoprotein-1 (beta(2)GP1). In th e postprandial state FVII is activated without apparent activation of FXII in plasma. We investigated whether beta(2)GP1, FXIIa and FVIIa ar e associated with triglyceride-rich lipoproteins in the fasting and po stprandial state. Six normal subjects were studied while fasting and 1 , 2 and 4 h after ingestion of 100 g fat. We confirmed that plasma FVI Ia activity, but not FXIIa antigen, was increased in the postprandial period. FXIIa, FVIIa and beta(2)GP1 were associated with chylomicra-ri ch lipoproteins, and lipase or Triton X-100 treatment caused an increa se in FXIIa in plasma and chylomicra without an increase in FVIIa. Thi s suggests that FXIIa may be formed in the postprandial period, but it s antigenic determinants are masked by the association with lipoprotei n particles, although it could still express proteolytic activity. Alt ernatively a FXII-independent mechanism or surface other than triglyce ride-rich lipoproteins may be responsible for FVII activation in the p ostprandial state. Blood Coag Fibrinol 9:323-332 (C) 1998 Lippincott-R aven Publishers.