Regulation of the metabolism of linoleic acid to arachidonic acid in rat hepatocytes.
When 5 X 10(6) hepatocytes were incubated for 40 min with from 0.15 to 0.60 mM [1-14C]linoleic acid, [1-14C]6,9,12-octadecatrienoic acid, or [1-14C]8,11,14-eicosatrienoic acid, there was a concentration-dependent acylation of radioactive metabolites into both triglycerides and phospholipids. When the concentration of either [1-14C]linoleic acid or [1-14C]8,11,14-eicosatrienoic acid exceeded 0.3 mM, there was no further increase in the metabolism of either fatty acid to other (n-6) metabolites. When the concentration of [1-14C]6,9,12-octadecatrienoic acid exceeded 0.15 mM, there was an apparent substrate-induced inhibition in its metabolism to 8,11,14-eicosatrienoic acid. With all three substrates (0.3 mM), there was time-dependent metabolism to other (n-6) acids. Cells then were incubated simultaneously with 0.3 mM [1-14C]linoleic acid along with 0.15 to 0.45 mM 6,9,12-octadecatrienoic acid or 8,11,14-eicosatrienoic acid. These exogenous nonradioactive (n-6) acids suppressed but did not abolish the conversion of [1-14C]linoleate to radioactive arachidonate. These findings suggest that some linoleate is converted to arachidonate without intracellular mixing of 6,8,12-octadecatrienoic or 8,11,14-eicosatrienoic acids. This hypothesis is supported by the finding that exogenous linoleate did not markedly affect the metabolism of [1-14C]6,9,12-octadecatrienoic or [1-14C]8,11,14-eicosatrienoic acid by microsomal chain elongating or desaturating enzymes.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000096:biosynthesis*; D008041:Linoleic Acids / Q000378:metabolism*; D008055:Lipids / Q000302:isolation & purification; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D001095:Arachidonic Acids; D008041:Linoleic Acids; D008055:Lipids; D016718:Arachidonic Acid