Uptake and utilization of double-labeled high-density lipoprotein sphingomyelin in isolated brain capillaries of adult rats.
Isolated rat brain capillaries were incubated in the presence of high-density lipoprotein (HDL) containing [stearic acid-14C, (methyl-3H)choline]sphingomyelin. This double-labeled sphingomyelin was taken up in a concentration-dependent manner. Cerebral capillary-associated sphingomyelin had a 3H/14C ratio close to that of the incubation medium, a result indicating uptake of sphingomyelin without prior hydrolysis. TLC of lipid extracted from capillaries showed that part of the sphingomyelin (up to 40%) was hydrolyzed in the brain capillaries to ceramide and free fatty acids. The hydrolysis was proportional to the amount of incorporated sphingomyelin and reached a plateau when the HDL sphingomyelin concentration in the medium was 237 nmol/ml. The results of "pulse-chase" experiments showed that the choline moiety of sphingomyelin was recovered in the incubation medium after the chase period and that there was no redistribution of liberated choline in phosphatidyl-choline of capillaries.
Homayoun
P
P
INSERM U. 26, Hôpital F. Widal, Paris, France.
Bentejac
M
M
Lecerf
J
J
Bourre
J M
JM
D000818:Animals; D002196:Capillaries / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002540:Cerebral Cortex / Q000098:blood supply; D002560:Cerebrovascular Circulation; D066298:In Vitro Techniques; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008297:Male; D010743:Phospholipids / Q000494:pharmacology; D011865:Radioisotope Dilution Technique; D051381:Rats; D013109:Sphingomyelins / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D008075:Lipoproteins, HDL; D010743:Phospholipids; D013109:Sphingomyelins; C037977:high density lipoprotein sphingomyelin; D014316:Tritium