[Effect of heparin on serum low density lipoproteins]

The effects of heparin on human serum low density lipoproteins (LDL) were studied by analytical ultracentrifugation. Precipitation of LDL without considerable alteration of the LDL micelles remaining in the solution was observed after addition of 1-10 micrograms of heparin to the samples containing 5 mg of LDL in 1 ml of 0.01 M Tris-buffer, pH 7.4, and 0.05% Na2-EDTA. The interaction between LDL and heparin was of electrostatic nature, i. e. it was inhibited by NaCl. The increase in the amount of the heparin added (up to hundreds micrograms) was accompanied by solubilization of the LDL precipitates; in the presence of certain concentrations of heparin the associates of LDL (apparently dimers) were formed. An addition of 1 mg of heparin to the samples containing 5 mg of LDL in 1 ml of the above buffer was accompanied by binding with the LDL of approximately 40 micrograms of heparin (data calculated from changes in the sedimentation co-efficients).