In vitro transfer of apolipoproteins from plasma lipoproteins to artificial lipid particles

Our earlier studies in vivo revealed that artificial lipid particles (exo TG) in lipid emulsion acquire apolipoprotein C-II (apo C-II) from high density lipoprotein (HDL). Since the transfer of apo C-II to exo TG terminated within a short time after the intravenous injection of exo TG, it is likely that exo TG has a high affinity for apolipoprotein. This hypothesis has been investigated in vitro. Human plasma was incubated at 37 degrees C with or without a 10% emulsion of soybean oil for 5 min and 60 min. After the incubation, the plasma was separated into HDL, low density lipoprotein (LDL) and very low density lipoprotein (VLDL). Levels of apo C-II, C-III and E in each lipoprotein fraction were quantified. When the plasma was incubated without exo TG, the distribution of apo C-II and C-III in the lipoprotein fractions was unchanged after incubations for 5 and 60 min. However, when the plasma was incubated with exo TG, apo C-II and C-III in the HDL fraction decreased after a 5 min incubation, while those in the VLDL fraction increased. Apo E in each lipoprotein fraction did not change after 5- and 60-min incubations regardless of the presence or absence of exo TG.(ABSTRACT TRUNCATED AT 250 WORDS)