Free Fatty Acids in the Rat Brain in Moderate and Severe Hypoxia

Abstract: The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial Po₂ 35–40 mm Hg) or moderate (Po₂ 25–30 mm Hg) hypoxia. The effects of severe hypoxia (Po₂ about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80–85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded that hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.     

Molecular Species of Phosphatidylcholine Containing Very Long Chain Fatty Acids in Human Brain: Enrichment in X-Linked Adrenoleukodystrophy Brain and Diseases of Peroxisome Biogenesis Brain

Molecular species of phosphatidylcholine containing unsaturated (i.e., monoenoic and polyenoic) 32- to 40-carbon (very long chain) fatty acids (VLCFA-PC) are present in normal human brain, the fatty acid composition changing significantly with development. There is a marked increase in the concentration and a change in the polyenoic VLCFA composition of these molecular species in brains of patients with inherited defects in peroxisomal biogenesis [Zellweger's syndrome, neonatal adrenoleukodystrophy (ALD), and infantile Refsum's disease]. In contrast, there is a marked increase in monoenoic VLCFA-PC in X-linked ALD whereas molecular species containing polyenoic VLCFA are minor components.     

胆碱摄取及磷脂酰胆碱合成的调节研究

木文研究了多种氨基酸、乙醇胺和甲基乙醇胺对细胞摄取胆碱和合成磷脂酰胆碱（ＰＣ）的影响,发现多种氨基酸非竞争性地抑制细胞摄取胆碱。含胆碱代谢物的分析显示胆碱转变成ＣＤＰ－胆碱,随之形成ＰＣ均不受氨基酸影响。乙醇胺竞争性地抑制胆碱摄取,且存在剂量依赖关系。乙醇胺能明显抑制胆碱激酶活性,但细胞内胆碱和磷酸胆碱的代谢池并不改变,提示乙醇胺不影响胆碱转变成磷酸胆碱。根据ＣＤＰ－胆碱和ＰＣ的比放射性分布,乙醇胺也不影响ＰＣ的生物合成。甲基乙醇胺抑制胆碱摄入的程度强于乙醇胺,并抑制胆碱激酶和ＣＴＰ：磷酸胆碱胞苷转移酶活性,含胆碱代谢物以ＣＤＰ－胆碱下降最显著;提示甲基乙醇胺不仅抑制胆碱摄入而且还干扰了ＣＤＰ－胆碱通路。     

Metabolic Turnover of Fatty Acids and Acylglycerols in Rat Sciatic Nerve

To explain the discrepancy between the low level and high metabolic activity of endoneurial free fatty acids (FFAs) and triacylglycerol (TG), levels of de novo synthesized FFA and acylglycerols were measured in rat sciatic endoneurium at various intervals after endoneurial microinjection of [14C]acetate. Soon after injection (less than 10 min), the [14C]acetate was metabolized to FFA and incorporated into diacylglycerol (DG), TG, sterols, ceramides, and various phospholipids. The proportions of 14C-labeled FFA, DG, TG, and ceramides to total 14C-labeled lipids decreased, whereas those of phospholipids and cerebrosides increased with time after injection. These findings suggest that rapid turnover of FFA and TG may contribute to their low level in sciatic endoneurium. The de novo synthesized fatty acids were largely incorporated into phosphatidylcholine (approximately 50% of total 14C-labeled phospholipids), probably via the cytidine nucleotide pathway using 1,2-DG as a metabolic intermediate. Hydrolysis of [14C]phosphatidylcholine revealed that fatty acids were labeled at both the C-1 (approximately 43%) and C-2 (approximately 57%) positions. On the other hand, a temporal association between decreased amounts of 14C-label in ceramides and increased amounts of 14C-label in sphingomyelin and galactocerebrosides supports the hypothesis that peripheral nerve galactocerebroside is derived, in vivo, from ceramide via acylation of sphingosine. This exclusive labeling of endoneurial lipids by endoneurial microinjection of labeled precursor provides a unique model for studying synthesis and metabolic turnover of membrane lipids in experimental neuropathies.     

Circannual Rhythm of Free Fatty Acids and Diacylglycerols in 5-Day-Old Rat Cerebrum During Pentylenetetrazol-Induced Convulsions

Free fatty acids (FFA) and diacylglycerol (DG) content and composition in the cerebrum of 5-day-old rats were studied after pentylenetetrazol (PTZ)-induced convulsions. A threefold increase in brain FFA was observed 30 min after PTZ injection in experiments carried out in spring. In contrast, a 50% decrease in FFA content was observed during summer. These changes were accounted for by saturated and monoenoic fatty acids, whereas arachidonic and docosahexaenoic acids were not affected during the convulsive episode in either season. The effect of PTZ on brain DG was much smaller than it was on FFA, and less sensitive to seasonal influence. However, DG released in the summer was significantly less enriched in arachidonic acid than in the spring. Levels of FFA and DG in untreated animals were found to be subject to a circannual rhythm. Both the levels of FFA and their degree of unsaturation (unsaturated fatty acids/total FFA) were highest in summer and lowest in winter, whereas the opposite was true for DG. Circannual variations in these metabolites may be the manifestation of a programmed biological calendar regulating enzymes of brain lipid metabolism in homeotherms that under natural conditions must adapt to changing environmental temperatures.     

Polyphosphoinositides as a Probable Source of Brain Free Fatty Acids Accumulated at the Onset of Ischemia

The quantitative relationship between phosphoinositides and free fatty acids (FFAs) in brain ischemia was studied by measuring contents of individual fatty acids in phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), phosphatidic acid (PA), diacylglycerol (DAG), and the FFA pool. Various periods of complete ischemia (1, 3, 10, and 30 min) were produced by decapitation. Ischemia of 1-3 min caused rapid decreases in PIP2 and PIP content together with preferential production of stearic and arachidonic acids in the DAG and FFA pools. The decrement in levels of these fatty acid residues in polyphosphoinositides was sufficient to account for their increment in levels in the enlarged DAG and FFA pools. After 10 min of ischemia, levels of PIP2, PIP, and DAG approached plateau values, but levels of all FFAs continued to increase. The increases in content of DAG and FFAs at later ischemic periods could not be accounted for by the decreases in content of PIP2 and PIP, PI and PA levels showed only transient and subtle changes. These results indicate that, at the onset of ischemia, phosphodiesteric cleavage of PIP2 and PIP and subsequent deacylation by lipases are primarily responsible for the preferential increase in levels of free stearic and arachidonic acids and that, later, hydrolysis of other phospholipids plays a major role in the continuous accumulation of FFAs.     

Evidence that 5'-Cytidinediphosphocholine Can Affect Brain Phospholipid Composition by Increasing Choline and Cytidine Plasma Levels

Abstract: We examined the effects of orally administered 5'-cytidinediphosphocholine (CDP-choline) on arterial plasma choline and cytidine levels and on brain phospholipid composition in rats. Animals receiving a single oral dose of 100, 250, or 500 mg/kg showed peak plasma choline levels 6–8 h after drug administration (from 12 ± 1 to 17 ± 2, 19 ± 2, and 24 ± 2 µ M , respectively). The area under the plasma choline curve at >14 µ M , i.e., at a concentration that induces a net influx of choline into the brain, was significantly correlated with CDP-choline dose. In rats receiving 500 mg/kg this area was 2.3 times that of animals consuming 250 mg/kg, which in turn was 1.8 times that of rats receiving 100 mg/kg. Plasma cytidine concentrations increased 5.4, 6.5, and 15.1 times baseline levels, respectively, 8 h after each of the three doses. When the oral CDP-choline treatment was prolonged for 42 and 90 days, brain phosphatidylcholine concentrations increased significantly (by 22–25%; p < 0.05) in rats consuming 500 mg/kg/day. Brain phosphatidylethanolamine and phosphatidylserine concentrations also increased significantly under some experimental conditions; levels of other phospholipids were unchanged.     

Quantification of Free Fatty Acids in Human Cerebrospinal Fluid

Free fatty acids (FFA) in cerebrospinal fluid (CSF) are well-recognized markers of brain damage in animal studies. Information is limited regarding human CSF in both normal and pathological conditions. Samples of CSF from 73 patients, who had undergone lumbar puncture for medically indicated reasons, came from a core laboratory upon completion of ordered tests. Using high performance liquid chromatography, mean FFA concentrations (g/L ± SEM) were: arachidonic 26.14 ± 3.44; docosahexaenoic 60.74 ± 5.70; linoleic 105.07 ± 10.98; myristic 160.38 ± 16.17; oleic 127.91 ± 10.13; and palmitic 638.34 ± 37.27. No differences in FFA concentrations were seen with gender, race, age, and/or indication for lumbar puncture. This is the first study to document normal human CSF FFA concentrations in a large series. Further characterization of FFA in pathological conditions may provide markers for evaluating clinical treatments and assisting in prognostication of neurological disease.     

Barbiturate Attenuation of Brain Free Fatty Acid Liberation During Global Ischemia

Abstract: To find a biochemical basis for the increased tolerance of the brain to anoxia during barbiturate anesthesia, we studied whole-brain free fatty acids (FFA) at various times after decapitation of awake and pentobarbital-anesthetized rats. Post-decapitation, the brains were kept at 37°C for 1 to 60 min before freezing in liquid N₂. Nonischemic brains were frozen in liquid N₂, using a rapid sampling technique. Whole-brain arachidonic, stearic, oleic, linoleic, and palmitic acids were quantitated by gas-liquid chromatography. In unanesthetized, nonischemic brain, total FFA was 1226 ± 121 nmol/g brain ( n = 12) and was unaffected by pentobarbital anesthesia (1126 ± 86 nmol/g brain, n = 11), except for a reduction in arachidonic acid. Total FFA in unanesthetized and pentobarbital-anesthetized rats transiently declined between 0 and 1 min of ischemia, and then rose linearly for up to 60 min, with consistently lower values in pentobarbital-treated rats, the greatest attenuation being that of arachidonic and stearic acid liberation. Brain FFA liberation during global ischemia is the first known biochemical variable directly correlated with the duration (i.e., severity) of global ischemia. The attenuation of brain FFA liberation and especially of arachidonic and stearic acids may be the biochemical basis of barbiturate attenuation of ischemic brain injury.     

Reassessment of Brain Free Fatty Acid Liberation During Global Ischemia and Its Attenuation by Barbiturate Anesthesia

Abstract: We previously reported that whole-brain free fatty acids (FFA) rose almost linearly for up to 1 h after decapitation of unanesthetized rats and was significantly attenuated by pentobarbital anesthesia. However, our values for total FFA and arachidonic, stearic, oleic, and palmitic acids were severalfold higher than those obtained by previous investigators. Based upon the suggestion that this may be due to FFAs released from di- and triglycerides in the quantitation of FFAs, we have now analyzed and improved our procedures for TLC separation of FFA and reassessed the accumulation of FFA in whole brain during decapitation ischemia in unanesthetized and pentobarbital-anesthetized rats. FFA levels in whole brain after 0.5 min of ischemia were one-half to one- fourth the levels previously reported after 1 min of ischemia. The rise in FFA between 0.5 and 60 min of ischemia was 9-fold for total FFA, and between 7 and 12-fold for each of the FFAs quantitated. Pentobarbital significantly attenuated the rise of all FFAs with, however, greater effects on oleic and palmitic acids than previously reported.     

液相色谱法定量检测老年人血浆游离脂肪酸

目的：分析老年人群空腹血浆游离脂肪酸水平及构成特点。方法：采用高效液相色谱（highperformanceliquidchromatog．raphy,HPLC）,检测149名60—104岁的健康老年人空腹血浆游离脂肪酸（FreeFattyacids,FFAs）的水平,包括月桂酸（C12：0）、二十碳五烯酸（C20：5）、豆蔻酸（C14：0）、软油酸（C16：1）、花生四烯酸（C20：4）、亚油酸（c18：2）、软脂酸（C16：0）、油酸（C18：1）和硬脂酸（C18：0）。结果：血浆FFA水平呈偏态分布;含量占血浆总FFA10％以上的单个FFA有3种,分别为：C16：0,C18：1和C18：2,共占总FFA的80％。结论：C16：0,C18：1和C18：2为血浆总FFA的主要组分,可体现血浆总FFA水平,并给出了健康老年人群的血浆总FFA及9种亚组分的均值、四分位数及中位数水平。     

Free Fatty Acid Content and Release Kinetics as Manifestations of Cerebral Lateralization in Mouse Brain

Free fatty acid (FFA) content was analyzed in mouse cerebral hemispheres and cerebellum under basal and postdecapitative ischemic conditions. Total FFA content immediately after decapitation (2 s) was about two-fold higher in the left hemisphere than in the right. Marked dissimilarities between hemispheres were also apparent when FFA levels were measured during short periods of ischemia. Whereas in the right side a significant FFA release took place as early as 10 s, no accumulation was detected in the left in the 2-20 s interval. The highest rates of total fatty acid release occurred in the 20-30 s interval in both hemispheres and decreased afterwards (3 min). Individual FFA, especially stearate and arachidonate, differed in their rates of production, the right cerebral hemisphere being more active in releasing arachidonic acid. In cerebellum, FFA levels were lower and accumulation was slower than in cerebrum in both intervals. When subjected to 3 min ischemia, the same difference in FFA levels between right and left hemispheres (50%) was observed in heads kept at 20 or 30 degrees C. The differences between hemispheres are interpreted as manifestations of an inherent lateralization in the regulation of acylation-deacylation reactions of complex lipids.     

Saccharomyces cerevisiae和Yarrowia lipolytica对自由饱和脂肪酸的选择性吸收及胞内积累特性研究

利用产油微生物生产特殊功能、高附加值的脂肪酸,具有良好的开发利用前景。以酿酒酵母(S.cerevisiae)和解脂耶氏酵母(Y.lipolytica)为出发菌株,以链长C4-C18的单一自由饱和脂肪酸作为唯一碳源,探究了两类酵母吸收利用、积累脂肪酸情况及胞内脂肪酸组成情况。结果表明:当碳链长C≤10时不能被利用,而且抑制细胞的生长,特别是当碳链长C≤8时,细胞很快被杀死;当碳链长C=11时,对细胞的生长有一定的抑制作用,菌体长势缓慢;碳链长C≥12时,对细胞生长没有影响;脂肪酸利用速度,偶数C脂肪酸奇数C脂肪酸;Nile red全细胞脂类染色显示,S.cerevisiae胞内脂质主要集中于胞内周边膜部位,Y.lipolytica主要以脂质体形式存在胞内,及少部分在胞内周边膜部位;GC/Mass脂类成分分析表明,菌株S.cerevisiae S228C BY4741-pox1和S.cerevisiae S228C BY4741-pox1,3可以积累培养基添加的相应脂肪酸,而其他供试菌积累的脂肪酸链长C≥16,没有检测到培养基含有相应的脂肪酸。这些结果为利用酵母生产特殊功能脂肪酸,及开发特色高附加值油脂提供了有意义的参考。     

硒、谷胱甘肽过氧化物酶和不饱和脂肪酸在鼠脑亚细胞中的分布

采用梯度离心和放射性同位素等方法从鼠脑中分离得到髓磷脂、突触囊、轻突触体、重突触体、线粒体６个亚细胞组分。分别测定了各亚细胞中硒－７５、谷胱甘肽过氧化物酶和不饱和脂肪酸的含量,结果表明这些成分在鼠脑亚细胞中的分布呈现明显的相关性,同时首次在突触囊、线粒体和微粒体中检测到三种不同的谷胱甘肽过氧化物酶的活性峰,其中之一可能是红细胞谷胱甘肽过氧化物酶（ＥＣ１．１１．１．９）．还就机体的自我保护机制和硒在脑组织中的重要作用进行了讨论。     

Utilization of Uniformly Labeled 13C-Polyunsaturated Fatty Acids in the Synthesis of Long-Chain Fatty Acids and Cholesterol Accumulating in the Neonatal Rat Brain

Abstract: Polyunsaturated fatty acids are needed for normal neonatal brain development, but the degree of conversion of the 18-carbon polyunsaturated fatty acid precursors consumed in the diet to their respective 20-and 22-carbon polyunsaturates accumulating in the brain is not well known. In the present study, in vivo ¹³C nuclear magnetic resonance spectroscopy was used to monitor noninvasively the brain uptake and metabolism of a mixture of uniformly ¹³C-enriched 16-and 18-carbon polyunsaturated fatty acid methyl esters injected intragastrically into neonatal rats. In vivo NMR spectra of the rat brain at postnatal days 10 and 17 had larger fatty acid signals than in uninjected controls, but changes in levels of individual fatty acids could not be distinguished. One day after injection of the U-¹³C-polyunsaturated fatty acid mixture, ¹³C enrichment (measured by isotope ratio mass spectrometry) was similar in brain phospholipids, free fatty acids, free cholesterol, and brain aqueous extract; ¹³C enrichment remained high in the phospholipids and cholesterol for 15 days. ¹³C enrichment was similar in the main fatty acids of the brain within 1 day of injection but 15 days later had declined in all except arachidonic acid while continuing to increase in docosahexaenoic acid. These changes in ¹³C enrichment in brain fatty acids paralleled the developmental changes in brain fatty acid composition. We conclude that, in the neonatal rat brain, dietary 16-and 18-carbon polyunsaturates are not only elongated and desaturated but are also utilized for de novo synthesis of long-chain saturated and monounsaturated fatty acids and cholesterol.     

Cerebral Phosphoinositide, Triacylglycerol, and Energy Metabolism in Reversible Ischemia: Origin and Fate of Free Fatty Acids

Levels of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), phosphatidic acid, diacylglycerol (DAG), triacylglycerol (TAG), and free fatty acids (FFAs), as well as their fatty acid composition, were determined in rat forebrain during ischemia and postischemic recirculation. Cerebral energy state and electroencephalograms (EEGs) were also studied. Fifteen minutes of ischemia resulted in a decrease in PIP2 and PIP contents but not in PI content, concurrent with an enlargement of the FFA and DAG pools. The latter were enriched in stearate and arachidonate. Prolongation of ischemia did not produce further changes in content of any of the inositol phospholipids, but the increase in levels of FFAs and DAG continued. At the end of 45 min of ischemia, levels of both PIP2 and PIP decreased by 45-50%, and the total phosphoinositide content (PIP2 + PIP + PI) decreased by 21%, whereas levels of FFAs and DAG increased to 14- and 3.6-fold of control levels, respectively. During ischemia, the TAG-palmitate level decreased, but the TAG-arachidonate level increased; the tissue energy state deteriorated severely; and the EEG was suppressed. A 30-min recirculation period after 15 or 45 min of ischemia led to increases in PIP2, PIP, and total phosphoinositide contents, whereas levels of FFAs and DAG promptly decreased toward control values. The TAG-arachidonate level peaked and the TAG-palmitate level returned to a low control value during early recirculation. The ischemic changes in tissue lipids were completely reversed within 3 h of recirculation after both periods of ischemia. Adenylates were fully phosphorylated with as little as 30 min of reflow. The EEG activity partially recovered during reflow after 15 min of ischemia, whereas it remained depressed after prolonged ischemia. Thus, phosphodiesteric cleavage of PIP2 and PIP followed by deacylation of DAG is likely to contribute to the production of FFAs in early ischemia. Deacylation of undetermined lipids plays a role for the increment in levels of FFAs in the later period of ischemia. The rapid postischemic increase in levels of PIP2 and PIP indicates active synthesis not only from existing PI, but probably also by means of accumulated FFAs and DAG. These results indicate that the impaired resynthesis of inositol phospholipids cannot be a cause of the poor EEG activity after prolonged ischemia. Degradation and resynthesis of polyphosphoinositides and formation of TAG-arachidonate may be important for modulation of free arachidonic acid levels in the brain during temporary ischemia.     

Arachidonic Acid Inhibits Choline Uptake and Depletes Acetylcholine Content in Rat Cerebral Cortical Synaptosomes

The effects of arachidonic acid on [3H]choline uptake, on [3H]acetylcholine accumulation, and on endogenous acetylcholine content and release in rat cerebral cortical synaptosomes were investigated. Arachidonic acid (10-150 microM) produced a dose-dependent inhibition of high-affinity [3H]choline uptake. Low-affinity [3H]choline uptake was also inhibited by arachidonic acid. Fatty acids inhibited high-affinity [3H]choline uptake with the following order of potency: arachidonic greater than palmitoleic greater than oleic greater than lauric; stearic acid (up to 150 microM) had no effect. Inhibition of [3H]choline uptake by arachidonic acid was reversed by bovine serum albumin. In the presence of arachidonic acid, there was an increased accumulation of choline in the medium, but this did not account for the inhibition of [3H]choline uptake produced by the fatty acid. Arachidonic acid inhibited the synthesis of [3H]acetylcholine from [3H]choline, and this inhibition was equal in magnitude to the inhibition of high-affinity [3H]choline uptake produced by the fatty acid. A K+-stimulated increase in [3H]acetylcholine synthesis was inhibited completely by arachidonic acid. Arachidonic acid also depleted endogenous acetylcholine stores. Concentrations of arachidonic acid and hemicholinium-3 that produced equivalent inhibition of [3H]choline uptake also produced equivalent depletion of acetylcholine content. In the presence of eserine, arachidonic acid had no effect on acetylcholine release. The results suggest that arachidonic acid may deplete acetylcholine content by inhibiting high-affinity choline uptake and subsequent acetylcholine synthesis. This raises the possibility that arachidonic acid may play a role in the impairment of cholinergic transmission seen in cerebral ischemia and other conditions in which large amounts of the free fatty acid are released in brain.     

Free Fatty Acids and Energy Metabolites in Ischemic Cerebral Cortex with Noradrenaline Depletion

Abstract: We tested whether cerebral noradrenaline (NA) may play a central role in mediating the increased production of free fatty acids (FFAs) during cerebral ischemia. Levels of FFAs, cyclic AMP, and NA, as well as ATP, ADP, and AMP, were measured in cerebral cortex during decapitation ischemia in rats 2 weeks after unilateral locus ceruleus lesion. Comparisons were made between the results obtained from the contralateral cortex with normal NA content and the NA-depleted ipsilateral cortex. Although NA depletion was associated with a diminished transient rise of cyclic AMP in response to ischemia, it failed to influence the magnitude of FFA increase or the decline of energy state within the 15-min period of ischemia. A more than twofold increase of total FFAs (sum of palmitic, stearic, oleic, arachidonic, and docosahexaenoic acids) was observed in both hemispheres at 1 min after decapitation, when energy failure became manifest. The increased production of FFAs continued throughout the 15 min of ischemia, with a preferential rise in the levels of stearic and arachidonic acids. There was an inverse correlation between FFA levels and total adenylate pool. The results do not support a major role for NA and cyclic AMP in increasing cortical FFAs during complete ischemia. Instead, they are consistent with the view that impaired oxidative phosphorylation activates deacylating enzymes. Disturbance of reacylation due to energy depletion is probably another factor contributing to the continuous increase of FFAs during prolonged ischemia.     

Free Fatty Acid Composition of Human and Rat Peripheral Nerve

Abstract: The free fatty acid (FFA) composition of peripheral nerve resembles that of erythrocytes but the composition of both is different from that of brain and other tissues. Approximately 75% of FFAs of nerve and erythrocytes are saturated and <5% are polyunsaturated whereas in brain and other tissues, 30-45% of FFAs are saturated and 25-50% are polyunsaturated. Approximately 10-15% of the total FFA of nerve have very long chain lengths [C₂₄, C₂₆, C₂₈, and C₃₀]. The presence of these very long-chain FFAs in endoneurium cannot be accounted for by the retention of erythrocytes or by lipid degradation. During Wallerian degeneration a significant increase of 18:1, associated with a decrease of saturated FFAs, was found in rat sciatic endoneurium, but normal values were approached when fiber regeneration was well under way. The FFA composition with chain length ≥C₂₆ were not, however, significantly altered with degeneration or repair of nerves. The metabolic significance of this striking difference between nerve and brain FFA composition is unknown but may reflect different functional properties.     

Relation Between Free Fatty Acid and Acyl-CoA Concentrations in Rat Brain Following Decapitation

To ascertain effects of total ischemia on brain phospholipid metabolism, anesthetized rats were decapitated and unesterified fatty acids and long chain acyl-CoA concentrations were analyzed in brain after 3 or 15 min. Control brain was taken from rats that were microwaved. Fatty acids were quantitated by extraction, thin layer chromatography and gas chromatography. Long-chain acyl-CoAs were quantitated by solubilization, solid phase extraction with an oligonucleotide purification cartridge and HPLC. Unesterified fatty acid concentrations increased significantly after decapitation, most dramatically for arachidonic acid (76 fold at 15 min) followed by docosahexaenoic acid. Of the acyl-CoA molecular species only the concentration of arachidonoyl-CoA was increased at 3 min and 15 min after decapitation, by 3–4 fold compared with microwaved brain. The concentration of docosahexaenoyl-CoA fell whereas concentrations of the other acyl-CoAs were unchanged. The increase in arachidonoyl-CoA after decapitation indicates that reincorporation of arachidonic acid into membrane phospholipids is possible during ischemia, likely at the expense of docosahexaenoic acid.