Secretion of alpha-tocopherol from cultured rat hepatocytes.
Primary cultures of rat hepatocytes and rat liver perfusions were used to study hepatic secretion of alpha-tocopherol. The secretion of alpha-tocopherol from hepatocytes in culture was linear with time for 4 h. Ultracentrifugation of the medium revealed that 89.4 +/- 2.1% of alpha-tocopherol secreted during 4 h incubation was associated with the very-low density lipoprotein fraction (VLDL, d less than 1.006 g/ml). Oleic acid had no significant effect on the secretory rate of alpha-tocopherol, whereas eicosapentaenoic acid reduced the amount of alpha-tocopherol secreted to 48.4 +/- 12.7% of the control value after 20 h incubation (P less than 0.01). Monensin, a known inhibitor of VLDL secretion, reduced the secretion of alpha-tocopherol to 14.1 +/- 4.3% of the control value (P less than 0.02). Colchicine and chloroquine inhibited the secretion of alpha-tocopherol in the same order of magnitude as monensin. Hepatic perfusion after intravenous injection of in vivo labeled alpha-[3H]tocopherol lymph, showed that about 75% of the secreted radioactivity was in the VLDL fraction. From these results we conclude that most alpha-tocopherol is secreted from the liver associated with nascent VLDL in rats.
Bjørneboe
A
A
National Institute of Forensic Toxicology, University of Oslo, Norway.
Bjørneboe
G E
GE
Hagen
B F
BF
Nossen
J O
JO
Drevon
C A
CA
D000818:Animals; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D003078:Colchicine / Q000494:pharmacology; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008985:Monensin / Q000494:pharmacology; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D014810:Vitamin E / Q000378:metabolism*
D009829:Oleic Acids; D014810:Vitamin E; D019301:Oleic Acid; D002738:Chloroquine; D008985:Monensin; D015118:Eicosapentaenoic Acid; D003078:Colchicine