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H Sprecher

Publications and source records attributed to H Sprecher.

At least 91 records · Page 5Linked to original sources
PubMed1989

The effect of a fish oil diet on the fatty acid composition of individual phospholipids and eicosanoid production by rat platelets.

When rats were fed a diet containing chow or fish oil for six weeks, the platelet phospholipid content and percent distribution were similar. In the fish oil fed animals there was a 54, 40, 41, and 24% reduction, respectively, in the levels of 20:4(n-6) in the choline-, ethanolamine-, inositol- and serine-containing glycerophospholipids. Dietary fish oil increased the total (n-3) polyunsaturated fatty acid content in all lipids. This effect was most pronounced in the ethanolamine glycerophospholipids which now contained 26, 11, and 4 nmols of 20:5(n-3), 22:5(n-3), and 22:6(n-3) in 10(9) cells. Ionophore A23187 stimulation of platelets from the chow fed rats resulted in the synthesis of 7, 64, and 3.5 nmols of 12-hydroxy-5,8,10-heptadecatrienoic acid, 12-hydroxy-5,8,10,14-eicosatetraenoic acid and 12-hydroxy-5,8,10,14,17-eicosapentaenoic acid, respectively, from 1 X 10(9) cells. The values from animals fed fish oil were 4, 18, and 27 nmol/10(9) platelets. It was not possible to detect any lipoxygenase products from 22:5(n-3) or 22:6(n-3), even though both acids are readily metabolized by lipoxygenase when added directly to platelets. These findings suggest that 22-carbon (n-3) fatty acids are not liberated when phospholipases are activated by calcium mobilization.

Animals↗
PubMed1989

Interactions between the metabolism of n-3 and n-6 fatty acids.

Dietary n-3 fatty acids modify the fatty acid composition of phospholipids of different cells and tissues from rats in diverse ways. Neutrophil and platelet phospholipids contain elevated amounts of 20:5n-3, but only relatively small changes occur in the levels of 22-carbon n-3 fatty acids. Conversely, dietary n-3 acids result primarily in an increase in 22-carbon n-3 acids in heart, liver and kidney phospholipids. Platelets metabolize exogenous n-6 and n-3 fatty acids into a variety of different autocoids. However, it appears that only arachidonate and 20:5n-3 are released from phospholipids upon agonist-induced stimulation of phospholipases. Neutrophils metabolize arachidonate and 20:5n-3 in similar ways, both relative to phospholipid biosynthesis and the subsequent release of these acids for metabolism into leukotrienes.

Animals↗
PubMed1989

Effect of a fish oil diet on the composition of rat neutrophil lipids and the molecular species of choline and ethanolamine glycerophospholipids.

When rats were fed a corn oil versus a corn oil-fish oil diet the overall phospholipid content and composition as well as the subclass distribution of the choline- and ethanolamine-containing glycerophospholipids from neutrophils were not altered. The serine-containing glycerophospholipids were characterized by high levels of stearic and oleic acids. When fish oil was added to the diet it replaced some of the arachidonate in both the inositol- and the serine-containing glycerophospholipids. In the corn oil-fed animals, 25.2 and 33.6 mole %, respectively, of the molecular species of 1,2-diacyl- and 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine contained arachidonate. The values for 1,2-diacyl and 1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine were, respectively, 41 and 55.8 mole %. When half of the 5% corn oil in the diet was replaced by fish oil, there was a 53, 38, 27, and 25% reduction, respectively, in the level of arachidonate in these four lipid subclasses. The amount of 5,8,11,14,17-eicosapentaenoic acid incorporated into these four subclasses was always less than the decline in arachidonic acid. This was due, in part, to the acylation of small amounts of 22-carbon (n-3) acids into these lipids. Molecular species analysis demonstrated that 5,8,11,14,17-eicosapentaenoic acid paired with the same components at the sn-1 position, and in the same ratio, as did arachidonic acid. The amounts of 16- and 18-carbon saturated and unsaturated fatty acid at the sn-2 position were not altered by dietary change. Collectively, these findings suggest that 5,8,11,14,17-eicosapentaenoic and arachidonic acids are metabolized in a similar way by neutrophils. These studies also support the concept that neutrophils contain two metabolic pools of phospholipids. One pool is altered by dietary fat change while the pool containing 16- and 18-carbon acids is resistant to change when fish oil is included in the diet.

Animals↗
PubMed1988

Metabolism of 6,9,12-octadecatrienoic acid and 6,9,12,15-octadecatetraenoic acid by rat hepatocytes.

When 5.10(6) hepatocytes were incubated for 40 min with 0.015-0.3 mM (1-14C)-labeled 6,9,12-octadecatrienoic acid or (1-14C)-labeled 6,9,12,15-octadecatetraenoic acid there was a concentration-dependent acylation of radioactive metabolites into both phospholipids and triacylglycerol. However, when the concentration of either substrate exceeded 60-150 microM there was no further increase in the metabolism of either substrate to longer-chain (n-6) and (n-3) acids. When cells were then incubated for various periods of time with 60 microM substrate there was initial rapid removal of the substrate which was accompanied by its acylation into lipids. Over time, the amount of both substrates in lipids declined without an overall drop in specific activity. This decline was accompanied by an increase in long-chain (n-6) and (n-3) fatty acids. Similar results were obtained when the time-dependent metabolism of the two substrates was examined in individual hepatocyte phospholipids. Collectively, these findings suggest that when these two 18-carbon acids are produced by desaturation of dietary linoleate and linolenate that they are in part initially acylated into a labile phospholipid pool. Rapid release and subsequent further metabolism to longer-chain (n-6) and (n-3) acids may explain why these products of the 6-desaturase do not accumulate in membrane lipids.

Animals↗
PubMed1988

Regulation of the metabolism of linoleic acid to arachidonic acid in rat hepatocytes.

When 5 X 10(6) hepatocytes were incubated for 40 min with from 0.15 to 0.60 mM [1-14C]linoleic acid, [1-14C]6,9,12-octadecatrienoic acid, or [1-14C]8,11,14-eicosatrienoic acid, there was a concentration-dependent acylation of radioactive metabolites into both triglycerides and phospholipids. When the concentration of either [1-14C]linoleic acid or [1-14C]8,11,14-eicosatrienoic acid exceeded 0.3 mM, there was no further increase in the metabolism of either fatty acid to other (n-6) metabolites. When the concentration of [1-14C]6,9,12-octadecatrienoic acid exceeded 0.15 mM, there was an apparent substrate-induced inhibition in its metabolism to 8,11,14-eicosatrienoic acid. With all three substrates (0.3 mM), there was time-dependent metabolism to other (n-6) acids. Cells then were incubated simultaneously with 0.3 mM [1-14C]linoleic acid along with 0.15 to 0.45 mM 6,9,12-octadecatrienoic acid or 8,11,14-eicosatrienoic acid. These exogenous nonradioactive (n-6) acids suppressed but did not abolish the conversion of [1-14C]linoleate to radioactive arachidonate. These findings suggest that some linoleate is converted to arachidonate without intracellular mixing of 6,8,12-octadecatrienoic or 8,11,14-eicosatrienoic acids. This hypothesis is supported by the finding that exogenous linoleate did not markedly affect the metabolism of [1-14C]6,9,12-octadecatrienoic or [1-14C]8,11,14-eicosatrienoic acid by microsomal chain elongating or desaturating enzymes.

Animals↗
PubMed1987

On the mechanism of action of xanthine oxidase. Evidence in support of an oxo transfer mechanism in the molybdenum-containing hydroxylases.

The mechanism of action of xanthine oxidase has been investigated using single-turnover experiments in an effort to determine the primary source of the oxygen atom incorporated into product in the course of catalysis. It is found from mass spectroscopic analysis of the uric acid generated in these experiments that when 16O-labeled enzyme in [18O]H2O is reacted with substoichiometric amounts of xanthine (under conditions where no enzyme molecule is likely to react with more than one substrate molecule), the uric acid isolated from the reaction mixture contains 16O at position 8 of the purine ring. Conversely, when 18O-labeled enzyme in [16O]H2O is exposed to substoichiometric xanthine, 18O is incorporated into the product uric acid. These results strongly support a variety of chemical studies with model molybdenum complexes suggesting that the oxygen atom of the Mo = O group known to be present at the active site of xanthine oxidase is transferred to product in the course of catalysis. The mechanistic implications of the present work are discussed.

Animals↗
PubMed1987

Metabolism of 8,11,14,17-eicosatetraenoic acid by human platelet lipoxygenase and cyclooxygenase.

Human platelets metabolize 8,11,14,17-eicosatetraenoic acid primarily into 12-hydroxy-8,10,14,17-eicosatetraenoic acid. Several other hydroxy acids were also produced in small amounts via an indomethacin insensitive pathway. Platelet cyclooxygenase metabolized this acid only into 12-hydroxy-8,10,14-heptadecatrienoic acid. It was not possible to detect any cyclic products even though vesicular gland cyclooxygenase metabolizes this (n-3) acid to 17,18-dehydroprostaglandin E1 (Oliw, E.H., Sprecher, H. and Hamberg, M. (1986) J. Biol. Chem. 261, 2675-2683).

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Very long chain (C24 to C36) polyenoic fatty acids of the n-3 and n-6 series in dipolyunsaturated phosphatidylcholines from bovine retina.

A complete series of even-carbon chain polyenoic fatty acids having 20-36 carbons occur in dipolyunsaturated molecular species of phosphatidylcholine from bovine retina. Using oxidative ozonolysis, it is shown that very long chain tetraenes belong to the n-6 series, hexaenes to the n-3 series, and major pentaenes to the n-3 series of fatty acids (very long chain n-6 pentaenes also occur). Molecular ions are obtained by electron impact mass spectrometry of methyl ester derivatives which conclusively identify the major components of this novel group of fatty acids. Mass spectral patterns are similar for the major very long chain tetraenes, for the pentaenes, and for the hexaenes, but different for each group of unsaturation. Very long chain (C24 to C36) polyenes account for about half the weight (40 mol %) of the acyl chains of major dodecaenoic, undecaenoic, and decaenoic molecular species of bovine retina phosphatidylcholine, the other half being made up by docosahexaenoate (22:6 n-3).

Animals↗
PubMed1987

Formation of 8-hydroxyhexadecatrienoic acid by vascular smooth muscle cells.

Smooth muscle cells derived from the human umbilical vein produce four radioactive metabolites when they are incubated in culture with [3H]-12-hydroxyeicosatetraenoic acid. This conversion does not require the addition of an agonist for eicosanoid formation. The main product, which accounts for 60% of the radioactivity converted to these metabolites, has been identified as 8-hydroxyhexadecatrienoic acid.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Stereospecific induction of starfish oocyte maturation by (8R)-hydroxyeicosatetraenoic acid.

Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. This induction of meiotic divisions can be triggered also by four fatty acids: 5,8,11-20:3; 5,8,11,14-20:4 (arachidonic acid); 6,9,12,15-20:4; 5,8,11,14,17-20:5, all other fatty acids being completely inactive. This maturation triggered by eicosanoids occurs in the micromolar range and is facilitated by the presence of calcium. A variety of arachidonic acid derivatives (esters, epoxides, etc.) and metabolites (cyclooxygenase and lipoxygenase products) has been tested; the biological activity is restricted to 8-hydroxyeicosatetraenoic acid (8-HETE), other mono- and poly-HETEs being completely inactive. Maturation triggered by 8-HETE occurs around 10 nM and is insensitive to the presence of calcium. 8-HETE methyl ester and 8-hydroperoxyeicosatetraenoic acid are able to induce maturation at higher concentrations. Both (8S) and (8R) stereoisomers have been tested; the biological activity is strictly restricted to the (8R) isomer. 8-HETE triggers a complete maturation, i.e. maturation-promoting factor appearance, germinal vesicle breakdown, emission of the polar bodies, and formation of a female pronucleus. (8R)-HETE, but not (8S)-HETE, triggers the typical decrease in cyclic AMP concentration induced by 1-methyladenine and the burst of protein phosphorylation associated with maturation. Starfish oocytes oxidize exogenous arachidonic acid into 8-HETE and other HETEs. 8-HETE was identified, after high pressure liquid chromatography purification, by gas chromatography mass spectrometry. Furthermore, it was found that the starfish oocytes only produce the (8R)-HETE isomer. This highly stereospecific induction of oocyte maturation by (8R)-HETE suggests that this fatty acid, or a very closely related fatty acid, may play a role in the transduction of the 1-methyladenine message at the plasma membrane level.

Animals↗
PubMed1986

Active labeling of phosphatidylcholines by [1-14C]docosahexaenoate in isolated photoreceptor membranes.

Isolated bovine rod outer segments and photoreceptor disks actively incorporated [1-14C]docosahexaenoate (22:6) into phospholipids when incubated in the presence of CoA, ATP, and Mg2+. About 80% of the esterified fatty acid was in phosphatidylcholine (PC). Microsomal and mitochondrial fractions incorporated as much 22:6 as rod outer segments, but it was distributed among various phospholipids and neutral glycerides. The isolated photoreceptor membrane thus contains an acyl-CoA synthetase which activates the fatty acid and a docosahexaenoyl-CoA-lysophosphatidylcholine acyltransferase activity. The specific radioactivity of PC was higher in rod outer segments than in the other subcellular fractions. About 2/3 of the label in photoreceptor membrane PC was in its dipolyunsaturated molecular species and 1/3 in hexaenes. Dipolyunsaturated PCs showed high turnover rates of 22:6 in all three subcellular membranes, especially in mitochondria. Retinal membranes in vitro seem to take up free [14C]22:6 from the medium by simple diffusion or partition into the membrane lipid. The ability of these membranes to activate and esterify [1-14C]22:6 indicates that docosahexaenoate-containing molecular species of retina lipids, including those of photoreceptor membranes, are subject to acylation-deacylation reactions in situ.

Animals↗
PubMed1986

Calcium-dependent oxidation of 5,8,11-icosatrienoic acid by the cyclooxygenase enzyme system.

Mead (5,8,11-icosatrienoic) acid was found to be metabolized by the cyclooxygenase enzyme system of ram seminal vesicle microsomes in a calcium-dependent manner. Although the enzyme converted Mead acid to products more slowly and less completely than the isomeric 8,11,14-icosatrienoic acid, both oxidations were inhibitable by indomethacin. Experiments using purified cyclooxygenase confirmed the participation of this enzyme system in the calcium-dependent oxidation. The products of the oxidation were separated by high performance liquid chromatography and analyzed by ultraviolet and gas chromatography-mass spectrometry. The spectra obtained were consistent with the products having the structures 13-hydroxy-5,8,11-icosatrienoate (the major product), 11-hydroxy-5,8,12-icosatrienoate, 9-hydroxy-5,7,11-icosatrienoate, and two isomeric 8,11-dihydroxy-5,9,12-icosatrienoates. No prostaglandin-like, cyclized products could be identified. This report is only the second to illustrate a calcium-dependent oxidation of a polyunsaturated fatty acid by a cyclooxygenase enzyme system and further extends the metabolic potential of Mead acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1986

Isolation of two novel E prostaglandins in human seminal fluid.

cis-8,11,14,17-[1-14C]Eicosatetraenoic acid was incubated with microsomes of ram seminal vesicles and 1 mM glutathione for 3 min at 37 degrees C. The main metabolite was identified as 17,18-dehydroprostaglandin E1 by capillary column gas chromatography-mass spectrometry. Human seminal fluid was analyzed for the presence of 17,18-dehydroprostaglandin E1 and prostaglandin E3. Whereas prostaglandin E3 could be demonstrated by capillary gas chromatography-mass spectrometry, 17,18-dehydroprostaglandin E1 could not be found under these conditions. However, human seminal fluid contained two compounds with a similar polarity on reversed phase high performance liquid chromatography as 17,18-dehydroprostaglandin E1 and prostaglandin E3. The two compounds were identified as 18,19-dehydroprostaglandin E1 and 18,19-dehydroprostaglandin E2 by gas chromatography-mass spectrometry, by UV analysis after conversion to the corresponding prostaglandin B compounds, and by ozonolysis. The amount of each of the two prostaglandins in human seminal fluid seemed to be in the same order of magnitude as the amount of prostaglandin E3.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1986

The metabolism of (n-3) and (n-6) fatty acids and their oxygenation by platelet cyclooxygenase and lipoxygenase.

Arachidonic acid is the principal unsaturated acid in most membrane lipids. Membrane lipids also contain a variety of other (n-6) and (n-3) fatty acids. The amounts of (n-6) and (n-3) fatty acids in membrane lipids can be modified by dietary fat change. Our studies show that long chain (n-6) and (n-3) acids are metabolized by platelet lipoxygenase and cyclooxygenase. When cells are exposed to various agonists, a variety of unsaturated fatty acids may be released. Our studies show that they have the potential of modifying physiological function both by mediating arachidonic acid metabolism and as direct precursors for oxygenated metabolites which themselves may interact with specific receptors to regulate biological processes.

Animals↗
PubMed1986

Metabolism of (n-6) and (n-3) polyunsaturated fatty acids by human platelets.

Human platelets metabolize 7,10,13,16-docosatetraenoic acid and 4,7,10,13,16-docosapentaenoic acid into 22-carbon thromboxanes 19-carbon HHT analogs and 14-hydroxy fatty acids via the lipoxygenase pathway. Conversely the two analogous (n-3) acids, 7,10,13,16,19-docosapentaenoic acid and 4,7,10,13,16,19-docosahexaenoic acid, are metabolized only into a pair of isomeric 11- and 14-hydroxy fatty acids. These findings suggest that platelets may contain more than one lipoxygenase.

Blood Platelets↗
PubMed1986

Biosynthesis of a novel prostaglandin, delta 17-PGE1, in the ram.

The prostaglandin, delta 17-PGE1, was purified from extracts of ram seminal fluid by reversed phase high performance liquid chromatography (HPLC) and identified after conversion to delta 17-PGB1 by UV-analysis and by capillary column gas chromatography-mass spectrometry (GC-MS). It was also formed by incubation of a homogenate of ram vesicular glands. The amount of delta 17-PGE1 in the seminal fluid and in the homogenate averaged 12% and 25% of the amount of PGE2, respectively. The results show that cis-8,11,14,17-eicosatetraenoic acid can be metabolized to prostaglandins in vivo in the ram.

Alprostadil↗