Molecular species of phosphoglycerides in liver microsomes of rats fed a fat‐free diet

Garda, Horacio Alberto; Bernasconi, Ana M.; Tricerri, M. Alejandra; Brenner, Rodolfo R.

doi:10.1007/s11745-997-0065-5

Cited by 6 publications

(9 citation statements)

References 27 publications

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“…As reported in other experiments (34,36,37), the predominant liver microsomal PtdCho species in control rats was found to be 18:0/20:4n-6 followed by 16:0/20:4n-6 and 16:0/18:2n-6.…”

Section: Resultssupporting

confidence: 83%

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Effect of dexamethasone on the fatty acid composition of total liver microsomal lipids and phosphatidylcholine molecular species

Brenner

Ayala

Garda

2001

Lipids

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Dexamethasone depresses delta6 and delta5 and increases delta9 desaturase and synthase activities. Therefore, we investigated the effect on the fatty acid composition of microsomal liver lipids and phosphatidylcholine (PtdCho) molecular species. After 15 d of treatment we found a notable decrease in arachidonic acid, a small decrease in stearic acid, and increases of linoleic, oleic, palmitoleic, and palmitic acids in liver microsomal total lipids and PtdCho. The study of the distribution of the PtdCho molecular species indicated that 18:0/20:4n-6, 16:0/20:4n-6, and 16:0/18:2n-6 predominated in the control animals. Dexamethasone, as expected because of its depressing effect on arachidonic acid synthesis and activation of oleic and palmitic acid synthesis, evoked a very significant decrease in 18:0/20:4n-6 PtdCho (P<0.001) and an important increase in 16:0/18:2n-6. The invariability of 16:0/20:4n-6 PtdCho could be related to the antagonistic effect of arachidonic and palmitic acid synthesis. PtdCho species containing oleic acid were not significant. The bulk fluidity and dynamic properties of the microsomal lipid bilayer measured by fluorometry using the probes 1,6-diphenyl-1,3,5-hexatriene and 4-trimethylammonium-phenyl-6-phenyl-1,3,5-hexatriene showed no significant modification, probably owing to a compensatory effect of the different molecular species, but changes of particular domains not detected by this technique are possible. However, the extremely sensitive Laurdan detected increased lipid packing in the less-fluid domains of the polar-nonpolar interphase of the bilayer, possibly evoked by the change of molecular species and cholesterol/phospholipid ratio. The most important effect found is the decrease of arachidonic acid pools in liver phospholipids as one of the corresponding causes of dexamethasone-dependent pharmacological effects.

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“…As reported in other experiments (34,36,37), the predominant liver microsomal PtdCho species in control rats was found to be 18:0/20:4n-6 followed by 16:0/20:4n-6 and 16:0/18:2n-6.…”

Section: Resultssupporting

confidence: 83%

“…As already found in other experiments (34,36,37), the highly predominant PtdCho species in the rat liver microsomes were 18:0/20:4n-6, 16:0/20:4n-6, and 16:0/18:2n-6. They were the principal determinants of the contribution of this phospholipid to the general biophysical properties and some of the chemical properties of the bilayer.…”

Section: Discussionsupporting

confidence: 85%

Effect of dexamethasone on the fatty acid composition of total liver microsomal lipids and phosphatidylcholine molecular species

Brenner

Ayala

Garda

2001

Lipids

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“…Therefore, the substitution of 20:4-containing species by 18:1-containing species nearly compensates for the fluidizing effect. These results are similar to ones found in the molecular species of all phosphoglycerides of hepatic microsomal lipids of rats fed on a fat-free diet (33). Although the effect in this case was due not to cholesterol but to a dietary deficiency of fats that evoked an essential fatty acid-deficient status, the change in the availability of fatty acids to build up the membrane phospholipids was rather similar.…”

Section: Discussionsupporting

confidence: 88%

“…As it is known, whereas saturated acids produce less fluid phospholipids with increasing chain length (20,33), polyunsaturated acids evoke only slightly more fluid liposomes than monounsaturated ones (34). Therefore, the substitution of 20:4-containing species by 18:1-containing species nearly compensates for the fluidizing effect.…”

Section: Discussionmentioning

confidence: 96%

Dietary cholesterol induces changes in molecular species of hepatic microsomal phosphatidylcholine

Bernasconi

Garda

Brenner

2000

Lipids

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After 21 days on a diet containing 1 g% cholesterol and 0.5 g% cholic acid, rats had an increased content of cholesterol in liver microsomal lipids. In liver, both cholesterol content and delta9 desaturase activity increased, whereas delta6 and delta5 desaturase activities decreased. These changes correlated with increases in oleic, palmitoleic, and linoleic acids and decreases in arachidonic and docosahexenoic acids in total microsomal lipids. Similar fatty acid changes were found in phosphatidylcholine (PC), the principal lipid of the microsomal membrane. In PC the predominant molecular fatty acid species (67% of the total) in the control rats were 18:0/20:4, 16:0/20:4, and 16:0/18:2; and they mainly determined the contribution of PC to the biophysical and biochemical properties of the phospholipid bilayer. The cholesterol diet decreased specifically the 18:0/20:4 species, and to a lesser extent, 16:0/20:4 and 18:0/22:6. The 18:1-containing species, especially 18:1/18:2 and less so 16:0/18:1 and 18:1/20:4, were increased. A new 18:1/18:1 species appeared. The independent effects of the presence of cholesterol and change of the fatty acid composition of the phospholipid bilayer of liver microsomes on the packing were studied by fluorescence methods using 6-lauroyl-2,4-dimethylaminonaphthalene, 1,6-diphenyl-1,3,5-hexatriene and 1-(4-trimethylammonium phenyl)-6-phenyl-1,3,5-hexatriene, which test different parameters and depths of the bilayer. Data showed that the increase of cholesterol in the membrane, and not the change of the fatty acid composition of phospholipids, was the main determinant of the increased bulk packing of the bilayer. The increase of fluid oleic- and linoleic-containing species almost compensated for the drop in 20:4- and 22:6-containing molecules. But the most important effect was that the general drop in essential n-6 and n-3 polyunsaturated fatty acids meant that this endogenous source for the needs of the animal decreased.

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“…Similarly, an in vitro study of cultured lung fibroblasts using 14 C-labeled fatty acids showed that 20:3n-6, 20:4n-6, and 20:5n-3 were incorporated somewhat differentially into various PL classes, with 20:3n-6 enriched in phosphatidylethanolamine (PE) and phosphatidylglycerol, 20:5n-3 enriched in PC, PE, and phosphatidylinositol (PI), and 20:4n-6 enriched in PC (55). In rat liver microsomes (56,57), 18:2n-6 was enriched in PC and PE, 20:3n-6 was incorporated mainly into PC, PE, and PI, and 20:4n-6 occurred primarily in PI, whereas C22 fatty acids (i.e., 22:4n-6, 22:5n-6, 22:5n-3, and 22:6n-3) were enriched in PE. In pig microsomes, 20:5n-3 was found mainly in PC (58).…”

Section: Different Lipid Classesmentioning

confidence: 99%

In vivo conversion of 18- and 20-C essential fatty acids in rats using the multiple simultaneous stable isotope method

Lin

Salem

2005

Journal of Lipid Research

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An important question for mammalian nutrition is the relative efficiency of C18 versus C20 essential fatty acids (EFAs) for supporting the tissue composition of n-3 and n-6 pathway end products. One specific question is whether C22 EFAs are made available to tissues more effectively by dietary ␣ -linolenic acid (18:3n-3) and linoleic acid (18:2n-6) or by dietary eicosapentaenoic acid (20:5n-3) and dihomo-␥ -linolenic acid (20:3n-6). To address this question in a direct manner, four stable isotope compounds were given simultaneously in a novel paradigm. A single oral dose of a mixture of 2 H 5 -18:3n-3, 13 C-U-20:5n-3, 13 C-U-18:2n-6, and 2 H 5 -20:3n-6 was administered to rats given a defined diet. There was a preferential in vivo conversion of arachidonic acid (20:4n-6) to docosatetraenoic acid (22:4n-6) and of 22:4n-6 to n-6 docosapentaenoic acid (22:5n-6) when the substrates originated from the C18 precursors. However, when the end products docosahexaenoic acid (22:6n-3) or 22:5n-6 were expressed as the total amount in the plasma compartment divided by the dosage, this parameter was 11-fold greater for 20:5n-3 than for 18:3n-3 and 14-fold greater for 20:3n-6 than for 18:2n-6. Thus, on a per dosage basis, the total amounts of n-3 and n-6 end products accreted in plasma were considerably greater for C20 EFA precursors relative to C18. -Lin, Y. H., and N. Salem, Jr. In vivo conversion of 18-and 20-C essential fatty acids in rats using the multiple simultaneous stable isotope method. J. Lipid Res. 2005Res. . 46: 1962Res. -1973

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Molecular species of phosphoglycerides in liver microsomes of rats fed a fat‐free diet

Cited by 6 publications

References 27 publications

Effect of dexamethasone on the fatty acid composition of total liver microsomal lipids and phosphatidylcholine molecular species

Effect of dexamethasone on the fatty acid composition of total liver microsomal lipids and phosphatidylcholine molecular species

Dietary cholesterol induces changes in molecular species of hepatic microsomal phosphatidylcholine

In vivo conversion of 18- and 20-C essential fatty acids in rats using the multiple simultaneous stable isotope method

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