Are ‘precipitated LDL’ really low density lipoproteins?

Cholesterol, phospholipid and Apo B levels were determined in low density lipoproteins (LDL) precipitated by amphipathic polymers (Biomerieux kit, Marcyl'Etoile, France) and compared to those of ultracentrifuged LDL. For 113 sera (triglyceride level < 4.5 mmol/l, absence of very low density lipoproteins-remnants) LDL-cholesterol values were significantly higher (p < 0.001), and those of LDLphospholipids (p < 0.001) and LDL-Apo B (p < 0.005) significantly lower. The correlations between the 3 constituents studied gave statistically different regression coefficients for the two methods. It is likely that discrepancy in results is due to the effect of ultracentrifugation and precipitation removing from the lipoprotein spectrum different sections which nonetheless have some common physicochemical or immunological properties. It would seem that the term ‘LDL’ is inappropriate to designate these precipitated lipoproteins.