HEMOSTATIC FACTORS IN RABBIT LIMB LYMPH - RELATIONSHIP TO MECHANISMS REGULATING EXTRAVASCULAR COAGULATION

Mechanisms regulating extravascular coagulation in interstitial fluids of peripheral tissues are poorly understood, since measurements of he mostatic factors in these fluids are unavailable. Because lymph from a body region reflects the composition of its interstitial fluid, we me asured hemostatic factors in limb lymph of rabbits both as activity an d as antigen. Mean lymph-to-plasma activity ratios were the following: fibrinogen, 0.28; prothrombin, 0.26; factor X, 0.27; factor VII, 0.17 ; and factors V and VIII, 0.08. All lymph fibrinogen was clottable; fi brin degradation products were absent. Lymph von Willebrand factor ant igen was <10% of plasma antigen and consisted primarily of lower molec ular weight multimers. Mean lymph-to-plasma activity ratio for antithr ombin was 0.38 and for tissue factor pathway inhibitor the ratio was 0 .40. Low levels of antithrombin-factor Xa were measurable in lymph. Th e data are compatible with a basal factor VIIa-tissue factor-catalyzed extravascular activation of factor X that is prevented from progressi ng to generation of fibrin in limb interstitial fluid and lymph by low levels of factor VIII and factor V and by the inhibitory activity of antithrombin and tissue factor pathway inhibitor.