Lipoprotein (a) is not a metabolic product of other lipoproteins containing apolipoprotein B.
125I-Labeled autologous very low density lipoprotein (VLDL) was injected intravenously into three lipoprotein (a) positive individuals. One other lipoprotein (a) positive subject received 125I-labeled VLDL from a a lipoprotein (a) negative donor. Specific activity of apolipoprotein B in VLDL, low density lipoprotein (LDL) and lipoprotein (a) was measured for 5 days. In the lipoprotein (a) fraction only traces of radioactivity could be detected, which were caused by contamination with labeled LDL. No precursor-product relationship existed between apolipoprotein B in VLDL or LDL and apolipoprotein B in lipoprotein (a). One lipoprotein (a)-positive individual was kept on a fat-free diet for 4 days to prevent chylomicron formation; no change in the serum level of lipoprotein (a) could be detected under these conditions. The data of this study indicate that lipoprotein (a) is not a metabolic product of VLDL or LDL. Also chylomicrons are not likely to play role as a precursor for lipoprotein (a). It is concluded that lipoprotein (a) is synthesized as a separate lipoprotein.
D000328:Adult; D000368:Aged; D001053:Apolipoproteins / Q000378:metabolism*; D002914:Chylomicrons / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged
D001053:Apolipoproteins; D002914:Chylomicrons; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL