PLASMA MACROMOLECULAR PROTEIN COMPLEX - INTERACTION WITH FIBRIN AND FIBRINOLYSIS

Fibrin and fibrin-like intravascular deposits are commonly observed in various diseases such as atherosclerosis (1-3) and diabetic nephropat y (4). In all these instances fibrin deposition was associated with in creased concentration of plasma fibrinogen (Fbg). It is presently reco gnized that elevated plasma Fbg is an important factor contributing to thrombosis and atherosclerosis (5). The elevated plasma Fbg level wou ld, however, only marginally increase the rate of intravascular fibrin deposition in the concentration range of about 1 to 4 mg/ml. This sug gests that there must be some other factor(s) which contribute to the thrombotic state. In the present paper we describe an unidentified pro tein from human plasma, termed a macromolecular protein complex (MPC), which is distinct from Fbg by size exclusion chromatography and heat stability at 56 degrees C. A characteristic property of MPC is the abi lity to become incorporated into a fibrin clot and to inhibit fibrinol ysis induced with plasminogen activators. The determination of Fbg con centration in diabetic plasma by functional and immunologic methods re vealed significant discrepancies between these two methods. This is ex plained by the presence of increased levels of MPC in diabetes. The re sults of this study suggest that MPC may be a new thrombogenic factor contributing to the increased tendency of cardiovascular complications in diabetes mellitus.