Acetate-1-14C incorporation into polyunsaturated fatty acids of phospholipids of developing chick brain

The incorporation of acetate-1-(14)C into the polyunsaturated fatty acids of glycerophosphatides of chick embryonic brain has been studied. After the injection of acetate-1-(14)C into the yolk sac, differences were found in the degree of labeling of the major fatty acids of the omega3 and omega6 series. Arachidonic acid (20:4omega6) showed a high degree of radioactivity while docosahexaenoic acid (22:6omega3) was poorly labeled, at a period of brain development when both fatty acids were being actively deposited. Evidence is presented to indicate that the low activity in docosahexaenoic acid is not explicable on the basis of either a low or high rate of turnover of this polyenoic acid. Similar results were obtained whether the rapid early or slower late stage of brain development was examined. It is suggested that the elongation of omega3 and omega6 series acids may be under the control of different regulatory mechanisms.     

Incorporation of [1-14C]acetate into the fatty acyl groups of soybean root plasma membrane phospholipids

The incorporation of [¹⁴C]acetate into fatty acids in a plasma membrane enriched fraction from mature soybean root (Glycine max) was studied by time-course experiments. Mature sections of 4-day-old dark-grown soybean roots were incubated with [1-¹⁴C]acetate, 1 mM sodium acetate and 50 μ/ml chloramphenicol. Plasma membrane vesicles were isolated at pH 7.8 and in the presence of 5 mM EDTA, 5 mM EGTA and 10 mM NaF. Lipid extracts analysed for phospholipid class and acyl chain composition revealed that relatively long incubation times did not alter the phospholipid composition of the plasma membrane enriched fraction. Radioactivity was incorporated into all the phospholipid classes proportional to their concentration in the membrane fraction. The distribution of ¹⁴C within the fatty acids of phosphatidylcholine and phosphatidylethanolamine differed from the respective fatty acid compositions and changed with time. Radioactivity also appeared more rapidly in the unsaturated acyl groups of phosphatidylcholine when compared with phosphatidylethanolamine. The rate and pattern of fatty acid incorporation into phosphatidylcholine differed from that for phosphatidylethanolamine.     

In vitro and in vivo synthesis of long-chain fatty acids from (1-14C) acetate in the renal papillae of rats.

1. The relationship between the rate of [1-14C] acetate incorporation into the fatty acids of renal papillary lipids and the acetate concentration in the medium has been measured. 2. [1-14C] acetate was incorporated mainly into fatty acids of phospholipids and triacylglycerols. Only a few per cent of the radioactivity was found in the free fatty acid fraction. 3. The major part of the [1-14C] acetate was found to be incorporated by a chain elongation of prevalent fatty acids. The major component of the poly-unsaturated fatty acids in triacylglycerols and the major product of fatty acid synthesis from [1-14C] acetate in vitro was demonstrated by mass spectrometry to be docosa-7,10,13,16-tetraenoic acid. 4. The radioactivity of docosa-7,10,13,16-tetraenoic acid accounted for 40% of total radioactivity in triacylglycerol fatty acids (lipid droplet fraction) and 20% of total radioactivity in membrane phospholipid fatty acids.     

Incorporation of ( 14 C)choline into phospholipids in the isolated phrenic nerve-diaphragm preparation of the rat

Abstract— The metabolism of [¹⁴C]choline has been studied in the isolated perfused phrenic nerve-diaphragm of the rat. We obtained no evidence that acetylcholine was synthesized from labelled choline in this system. There was extensive incorporation of the choline into phosphatidylcholine and its precursors, cytidinediphosphocholine (CDP-choline) and phosphocholine. Autoradiographic studies indicated that the lipids of myelin sheaths and nerve endings were the primary sites labelled.     

Incorporation of radioiodinated fatty acids into cardiac phospholipids of normoxic canine myocardium

The aim of this study was to assess the phospholipid distribution of radioiodinated 17-iodoheptadecanoic acid (IHDA), 15-(p-iodophenyl)pentadecanoic acid (p-IPPA) and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) under normoxic conditions and to compare these data with the fatty acid composition of the phospholipid classes. After simultaneous i.v. injection of the radioiodinated fatty acids (1-123-IHDA; 1-131-p-IPPA; 1-125 DMIPPA) in open-chest dogs seven myocardial biopsies were taken over 40 min (n = 26). After lipid extraction of the biopsies the organic phase was analyzed for both neutral and polar lipids by two different TLC systems. The following polar lipid fractions were analyzed: lysophopshatidylcholine (LPC), sphingomyelin (SPH), phosphatidy1choline (PC; lecithin), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG; cardiolipin) and neutral lipids. Fractions were counted in a gamma well counter and corrected for cross-over and recovery. Results of the polar phospholipids analysis showed that IHDA has the highest incorporation into the phospholipids. The IHDA was mainly incorporated into PI (45.6%) followed by PC (30.9%), PE (14.0%) and PS (5.6%). The p-IPPA was predominantly incorporated incorporated into PC (37.2%), followed by PS (20.1%) and PE (13.7%). In contrast to IHDA, incorporation of p-IPPA into PI was small (6.4%). The DMIPPA analogue was incorporated into phopsholipids to only a very small degree, compared to IHDA and p-IPPA. PS (27.4%) was the only considerable phospholipid fraction into which DMIPPA was incorporated.The results clearly demonstrated that these radioiodinated fatty acid analogues have entirely different patterns of phospholipid incorporation. Major resemblances have been found between the incorporation into phospholipids of IHDA and the phospholipid distribution of the natural counterpart: stearic acid. The p—IPPA phospholipid incorporation only partly resembles the phospholipid distribution of palmitic acid. DMIPPA is because of its modified structure, incorporated into phospholipids to a low extent, mainly into PS. (Mol Cell Biochem116: 79–87, 1992)