The rapid incorporation of radioactive fatty acid into triacylglycerols during the in vitro acylation of native lipids of neuronal nuclei.
Using neuronal nuclei (N1) and microsomes (P3) isolated from cerebral cortices of 15-day-old rabbits, the incorporation of [14C]oleate was followed in vitro, making use of fatty acid activation factors and endogenous membrane acyl acceptors. Of the lipids of N1, it was triacylglycerol which showed the highest rates of labelling and which represented 71-80% of the total incorporated radioactivity in this fraction. Specific rates of N1 triacylglycerol formation were 63-166 times those of P3 triacylglycerols (based upon membrane phospholipid content). In P3, phospholipids made up 85% of the total microsomal lipid labelling. The incorporation of oleate was dependent upon ATP and coenzyme A, and acyl-CoA synthetase activities were demonstrated in N1 and P3 (specific activity ratio, N1:P3 = 4.5). Using exogenous [14C]oleoyl-CoA, high rates of N1 triacylglycerol labelling were still seen relative to P3, but rates of diacylglycerol and phospholipid labelling were substantially elevated in both fractions in contrast to rates found using [14C]oleate. By increasing levels of endogenous diacylglycerol using preincubations with phospholipase C, a 3-fold increase was seen in specific rates of triacylglycerol formation in both fractions in subsequent assays with [14C]oleate. A 4.5-fold increase in N1 diacylglycerol concentrations was found when N1 was incubated for 10 min in the absence of fatty acid, ATP and coenzyme A. It is concluded that neuronal nuclei have a very active diacylglycerol acyltransferase as well as the ability to generate diacylglycerol substrates.
D000215:Acylation; D000818:Animals; D002250:Carbon Radioisotopes; D002467:Cell Nucleus / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism*; D066298:In Vitro Techniques; D007553:Isotope Labeling; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D011817:Rabbits; D014280:Triglycerides / Q000096:biosynthesis*
D002250:Carbon Radioisotopes; D008563:Membrane Lipids; D009829:Oleic Acids; D010743:Phospholipids; D014280:Triglycerides; D019301:Oleic Acid