Visual acuity of essential fatty acid-deficient rats

1. Rats were maintained on a diet deficient in fat and on a normal diet of rat cubes. 2. Rats were trained to discriminate between vertical and horizontal striations. The minimal stripe width that could be used for discrimination was determined. 3. In bright illumination (0·7 or 4·5 ft.lamberts) both deficient and normal rats had the same ability to discriminate between black and white stripes. 4. With an illuminance of 0·002 ft.lambert, supplemented rats could discriminate as efficiently as at 0·7 ft.lambert, but deficient animals were unable to discriminate at 0·002 ft.lambert. 5. Control rats had 14% of docosahexaenoic acid in their retinal fats but the deficient rats had only 1%. 6. Deficient animals had no vitamin A stores in the liver whereas the control animals had about 190 i.u./g. 7. The visual acuity of the rats used was about 45′ of arc.     

Leukotriene B formation by neutrophils from essential fatty acid-deficient rats

Analysis of neutrophil phospholipids from rats fed an essential fatty acid-deficient diet revealed a 33% reduction in arachidonate and a 90% reduction in linoleate compared to neutrophil phospholipids of rats fed a normal diet. The neutrophil phospholipids from rats fed the essential fatty acid-deficient diet also contained significant amounts of 5,8,11-eicosatrienoate, a fatty acid not found in the neutrophils of rats fed a normal diet. Analysis of the production of leukotrienes of the B series by ionophore-stimulated neutrophils from rats fed an essential fatty acid-deficient diet revealed a 87% reduction in leukotriene B4 compared to neutrophils from rats fed a normal diet even though the arachidonate content was reduced by only 34%. Essential fatty acid-deficient neutrophils converted endogenous 5,8,11-eicosatrienoic acid to leukotriene A3 and its nonenzymatic degradation products, but little or no leukotriene B3 was formed. Neutrophils from rats fed a normal diet incubated with ionophore and exogenous 5,8,11-eicosatrienoate also produced leukotriene A3 and its nonenzymatic degradation products but little or no leukotriene B3. Exogenous 5,8,11-eicosatrienoate incubated with ionophore-stimulated normal neutrophils caused a dose-dependent inhibition of leukotriene A hydrolase resulting in diminished production of leukotriene B4 from endogenous arachidonate. Assays of leukotriene A hydrolase in the 10,000 X g supernatant fraction of a homogenate of RBL-1 cells revealed that a lipoxygenase metabolite of 5,8,11-eicosatrienoate rather than 5,8,11-eicosatrienoate itself is the inhibitor of leukotriene A hydrolase. Thus the finding that leukotriene B4 production by neutrophils from essential fatty acid-deficient rats is diminished out of proportion to the decrease in arachidonate content appears to be due to inhibition of leukotriene A hydrolase by a lipoxygenase metabolite.     

In vitro accumulation of amino acids by intestinal strips from normal and essential fatty acid-deficient rats

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1. Steady-state accumulation of phenylalanine, leucine, glutamic acid and lysine by the small intestine from rats fed corn oil (control) or hydrogenated coconut oil (essential fatty acid-deficient) was studied by an in vitro technique.     

Turnover of mitochondrial components of normal and essential fatty acid-deficient rats

1. Essential fatty acid (EFA)-deficient and control rats were injected intraperitoneally with [(32)P]phosphate, l-[(35)S]methionine and [2-(14)C]acetate. The animals were killed at various time-intervals after injection and their liver mitochondria fractionated into soluble protein, insoluble protein, and lipid. 2. The (35)S was assayed in the protein fractions and (32)P and (14)C were assayed in the lipid fraction. Curves of log (specific activity) plotted against time were prepared for the different fractions. 3. There was no significant difference between the insoluble protein results for control and EFA-deficient animals, both sets of results indicating the presence of a single component of half-life 9 days. 4. There was no significant difference between the soluble protein results for the two sets of animals and both sets of results indicated the presence of at least two components. 5. The [(32)P]-phospholipid results indicate that in the control animals the liver mitochondrial phospholipids contain components of half-life 1.6 and 10 days whereas the mitochondrial phospholipids of the EFA-deficient animals contain components of half-life 3 and 29 days. 6. The specific activity of mitochondrial [(14)C]phospholipid initially fell rapidly in both groups of animals, but after 17 days there was no further significant decrease. A fast component with maximum half-life 2-4 days was clearly demonstrated for both groups of animals. Whether or not these results also indicate the presence of a very long-lived mitochondrial phospholipid is discussed.     

Effects of infusion of some prostaglandins in essential fatty acid-deficient and normal rats

Infusion of 1 mg/kg per day of prostaglandin E(1) (PGE(1)) for 2 and 7 wk failed to correct the dermal signs of essential fatty acid (EFA) deficiency in rats despite the known conversion of EFA to certain prostaglandins. PGE(1) caused no significant changes in serum cholesterol, triglycerides, or phospholipids or in liver neutral lipids in EFA-deficient or normal rats. In normal rats epinephrine-induced lipolysis was greater in fat pads from infused than from untreated rats. The effect on epinephrine-induced lipolysis was greater after the 7 wk infusion than after the 2 wk infusion. The 7 wk infusion also lowered plasma free fatty acid (FFA) concentrations. Infusion of PGE(2) and PGF(2alpha) in combination for 4 wk had no significant effect on either dermal signs of EFA deficiency, lipolysis, or plasma FFA concentrations.     

Apparent in vivo retroconversion of dietary arachidonic to linoleic acid in essential fatty acid-deficient rats

Essential fatty acid-deficient rats were fed ethyl [U-14C]arachidonate (308 dpm/nmol) and when a decrease in the transepidermal water loss was seen, the epidermal sphingolipids, acylglucosylceramide and acylceramide were isolated. [14C]Linoleic acid (approx. 130 dpm/nmol) was present in both lipid classes, while the substrate was only detected in the former. These results intimate that in vivo retroconversion of arachidonic to linoleic acid can be induced in the rat.     

Selective incorporation of n-3 and n-6 fatty acids in essential fatty acid deficient rats in response to short-term oil feeding

Essential fatty acid deficient male Sprague Dawley rats were fed for 7 days a fat-free semi-synthetic diet supplemented with 10% by weight of different oil supplements. The oil supplement was a mixture of olive, safflower and linseed oils prepared at different proportions so the dietary n-9/n-6/n-3 ratios were approximate 2/1/1, 1/2/1, 1/1/2, and 1/1/1. The fatty acid compositions of plasma and liver lipids were then examined. Our results show polyunsaturated n-6 and n-3 fatty acids were selectively incorporated into plasma and liver phospholipids, and also into plasma cholesteryl esters. A preferential incorporation of n-6 over n-3 fatty acids into plasma cholesteryl esters and phospholipids was also observed.     

Synthesis of cyclopropane fatty acids in isolated bacterial membranes

Isolated E. coli membrane vesicles can synthesize cyclopropane fatty acids from S-adenosylmethionine using endogenous membrane phospholipid as the lipidsubstrate. The major methylated products are methylenehexadecanoic acid and methyleneoctadecenoic acid esterified to phosphatidylethanolamine. The membrane system is slightly stimulated by sodium dodecyl sulfate at low concentrations but is inhibited by neutral surfactants. The reaction is inhibited by phospholipase C and phospholipase A. The Arrhenius plot for the enzyme reaction is discontinuous over the temperature range 0–35 °C.     

Location of double bonds and cyclopropane rings in fatty acids by mass spectrometry

Electron-impact mass spectrometric procedures for locating the position of double bonds and cyclopropane rings in long-chain fatty acids are reviewed. Since unsaturation is not located directly by mass spectrometry, the properties of suitable derivatives are summarized. Epoxides are readily prepared from double bonds and on opening of the ring with various reagents useful derivatives are obtained, the most promising to date being hydroxymethoxy esters whose trimethylsilyl ethers give good mass spectra. Trimethylsilyl ethers of vicinal diols, prepared by direct hydroxylation, are recommended for the analysis of polyunsaturated fatty acid esters using combined gas chromatography-mass spectrometry. Oxymercuration-demercuration techniques are very convenient and one particular procedure can specifically locate unsaturation up to five carbons distant from the carboxyl group. An alternative approach enables the location of double bonds and cyclopropane rings in fatty acids by direct mass spectrometry of pyrrolidides. Cyclopropane rings can be positively located in fatty acid esters by mass spectrometry of isomeric ketones or methoxy derivatives prepared by chromium trioxide oxidation on poron trifluoride-catalysed methoxylation, respectively. A variety of other procedures are also considered and some guidelines are given for choosing a method to suit a particular unsaturated acid.