The Formation of Chondromucoprotein-fibrinogen and Chondromucoprotein-beta-lipoprotein Complexes.

The literature contains numerous references to the formation of insoluble complexes when polysulphate and poly(carboxylic acid) macromolecules are added to various plasma and serum colloids. Chondroitin sulphate, for instance, precipitates complexes containing protein and cholesterol (Badin & Schubert, 1955; Kerby, Taylor & Langley, 1961). Heparin forms insoluble complexes with fibrinogen (Smith & Korff, 1957; Godal, 1961) and when added to plasma precipitates a complex containing fibrinogen and plasminogen (Green, 1962). The addition of hyaluronic acid (Serafini-Cessi, 1959) to guinea-pig serum forms precipitates containing fibrinolytic enzymes. Dextran sulphate (Walton, 1954) and sulphated starches (Bernfeld & Nisselbaum, 1956) form insoluble complexes with fibrinogen. The presence of -lipoprotein in precipitates formed between serum and heparin and between serum and various sulphate esters (including those of amylopectin, amylose, dextran and cellulose) has been reported (Bernfeld & Nisselbaum, 1956; Burstein, 1956; Bernfeld, Donahue & Berkowitz, 1957; Oncley, Walton & Cornwell, 1957). The formation of a complex also occurs between plasma ,B-lipoproteins and mucopolysaccharides isolated from both atherosclerotic (Ger6, Gergely, Jakab, Szekely & Virag, 1961) and normal (Amenta & Waters, 1960) human aorta. Fibrin, formed by the addition of thrombin to plasma, contains P-lipoproteins (Morrison, 1947). Many of these interactions, however, have been studied with substances either not normally present in the body or present in low concentrations. A large part ofthe chondroitin sulphate in cartilage, for instance, exists as chondromucoprotein in which chondroitin sulphate is bound covalently to non-collagenous protein (Shatton & Schubert, 1954; Partridge, Davis & Adair, 1961). Free chondroitin sulphate may not normally exist in the body, since even proteolytic attack by papain on chondromucoprotein preparations fails to remove all the bound amino acids (Muir, 1958). Also, viscometric studies on the digestion of chondromucoprotein by papain and by plasmin suggest that the enzymic products are smaller chondromucoprotein units (for which the name 'chondromucopeptide' is proposed) rather than free chondroitin sulphate (Anderson, 1962a). It was decided to investigate whether chondromucoprotein and chondromucopeptide possessed properties similar to those of chondroitin sulphate and other polysulphate and poly(carboxylic acid) polymers. The present study shows that the addition of chondromucoprotein to plasma, under specified conditions, forms insoluble complexes that contain a-, ,and y-globulins, P-lipoproteins, cholesterol, mucopolysaccharides and several components of the fibrinolytic system (fibrinogen, plasminogen and streptokinase proactivator). A preliminary report of part of this work has been published (Anderson, 1962c).