Dextran-induced lowering of plasminogen proactivator and functionally active high molecular weight kininogen in the rat.

Incubation of plasminogen-free rat citrated plasma with acetone (23% v/v) yielded enzyme preparations with high levels of plasminogen activator (PGA) and kininogenase (kallikrein), but with a low concentration of high molecular weight kininogen (HMWK) active as cofactor for kaolin-induced activation of factor XII. When benzamidine (4.0 mM) was present during acetone activation, a high yield of functionally active HMWK was obtained. Gel chromatography separated PGA into one high molecular weight fraction (HMW-PGA) without kininogenase and BAEe esterase activity, and one fraction (LMW-PGA) eluting together with plasma kallikrein. Injection of dextran (100 mg/kg intravenously) reduced the amount of LMW-PGA to 40%, without altering the concentration of HMW-PGA, and with only a small reduction of the kininogenase activity.