Metabolic fate of sphingomyelin of high-density lipoprotein in rat plasma.
The metabolic fate of high density lipoprotein (HDL) sphingomyelin in plasma was studied in rats over a 24-hr period after injection of HDL containing sphingomyelin which was 14C-labeled in the stearic (18:0) or lignoceric acid (24:0) moiety and 3H-labeled in the choline methyl groups. Decay of label in plasma followed three phases. The first two phases were similar for both isotopes and both types of sphingomyelin (t1/2 approximately 10 and 110 min). However, during the third phase (from 10 hr after injection), 3H label disappeared more slowly than 14C label from 18:0 sphingomyelin, whereas the 3H/14C ratio remained relatively constant when 24:0 sphingomyelin was used. Intact, doubly-labeled 18:0 sphingomyelin disappeared from HDL rapidly (t1/2 = 38 min) by tissue uptake and by transfer to very low density lipoprotein (VLDL). VLDL contained up to 12% of the sphingomyelin 1 hr after injection. This is the first demonstration of a transfer in vivo of sphingomyelin from HDL to VLDL. A similarly rapid transfer was also observed in vitro. Some nontritiated, [14C]18:0 or [14C]24:0 sphingomyelin was redistributed more slowly into HDL. Doubly-labeled phosphatidylcholine appeared in VLDL and HDL within 1 hr after injection and reached 1.8 and 2.1% of the injected 14C and 3H in VLDL at 1 hr, and 4.8 and 6.9% in HDL at 3 hr, respectively.
Bentejac
M
M
Laboratoire de Physiologie Animale et de la Nutrition, Faculte des Sciences Mirande, Universite de Dijon-BP 138, France.
Bugaut
M
M
Delachambre
M C
MC
Lecerf
J
J
D000818:Animals; D001923:Brain Chemistry; D002250:Carbon Radioisotopes; D002417:Cattle; D005227:Fatty Acids / Q000097:blood; D006207:Half-Life; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood*; D008079:Lipoproteins, VLDL / Q000097:blood; D008099:Liver / Q000378:metabolism; D008297:Male; D010713:Phosphatidylcholines / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D013109:Sphingomyelins / Q000097:blood*; D013229:Stearic Acids / Q000097:blood; D014316:Tritium
D002250:Carbon Radioisotopes; D005227:Fatty Acids; D008075:Lipoproteins, HDL; D008079:Lipoproteins, VLDL; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D013229:Stearic Acids; D014316:Tritium; C031183:stearic acid; C010210:lignoceric acid