the effect of phosphorylcholine in promoting the interaction between heparin and pure chylomicrons or very low density lipoproteins was regained when a crude serum protein factor of unwashed chylomicrons was added to the system , suggesting that rat serum contains a protein factor ( s ) which normally inhibits the heparin -- lipoprotein interaction by raising the requirement of ca2+ .
C0023825
very low density lipoproteins
C0023820
lipoprotein