Chylomicron apoprotein alteration after plasma exposure

Abstract

Purified rat lymph chylomicrons were incubated with chylomicron-free rat plasma and examined for changes in lipid and apoprotein constituents. Upon incubation there was a five-fold increase in the arginine rich apoprotein and a concomitant reduction in chylomicron Apo A-I to less than one-sixth its preincubation mass. These apoprotein changes were most faithfully reproduced when chylomicrons were incubated with the rat HDL fraction, although incubations of chylomicrons with rat lipoprotein-free plasma showed that arginine-rich apoprotein could readily associate with chylomicrons without concomitant changes in chylomicron lipid constituents. The gain in chylomicron apoprotein paralleled an increased affinity of the incubated chylomicron for heparin, when examined by heparin affinity chromatography. The apoprotein alterations were consistent in incubations in which the triglyceride concentrations varied from 330 mg/dl to 4200 mg/dl, and were not affected by inhibition of the Lecithin: Cholesterol Acyl Transferase (LCAT) reaction in the incubation mixture. The demonstration that in vivo alimentary lipemia chylomicrons have an apoprotein pattern identical to that of chylomicrons following in vitro plasma incubation suggests that these apoprotein alterations occur physiologically in alimentary lipemia.