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H Sprecher

Publications and source records attributed to H Sprecher.

At least 127 records · Page 7Linked to original sources
PubMed1983

Synthesis of hydroxy fatty acids from 4, 7, 10, 13, 16, 19-[1-14C] docosahexaenoic acid by human platelets.

Human platelets incubated in the presence of 54 microM [1-14C]22:6 produced hydroxydocosahexaenoic acid (HDHE) at about half the rate with which 12-hydroxy-5,8,10,14-eicosatetraenoic acid is produced from [1-14C]arachidonic acid. More than 90% of the radioactivity in HDHE was distributed among two major isomers, 14-HDHE and 11-HDHE. The production of HDHEs was unaffected by indomethacin but completely inhibited by 5,8,11,14-heneicosatetraynoic acid, which suggests that the hydroxy fatty acids are produced by lipoxygenase. The proportions of HDHE isomers varied with the concentration of 22:6. The ratio 14-HDHE/11-HDHE was higher at 6.8 microM 22:6 than when platelets were incubated with 54 microM 22:6. It is suggested that the amounts of these isomers produced will depend both on the availability of 22:6 as well as by competition of this acid with other acids for lipoxygenase.

Blood Platelets↗
PubMed1983

Potentiating effect of 5,8,11-eicosatrienoic acid on human platelet aggregation.

5,8,11-Eicosatrienoic acid (20:3 omega 9), a fatty acid increased in the platelet phospholipids of man and animals fed saturated fats, was either added to human platelets simultaneously with the aggregating agents, or incorporated into the platelet phospholipids by preincubation. 20:3 omega 9 markedly increased the response of platelets to all aggregating agents tested when added simultaneously with the agent, but solely to thrombin and ionophore, after incorporation into the platelet phospholipids. The potentiating effects of 20:3 omega 9 on thrombin aggregation do not appear to be related to prostaglandin formation, but rather to the production of a monohydroxy derivative through the lipoxygenase pathway.

8,11,14-Eicosatrienoic Acid↗
PubMed1983

High affinity esterification of eicosanoid precursor fatty acids by platelets.

We have examined the relative rates of uptake of several fatty acids into washed, human platelets by measuring incorporation into cellular phospholipids. In the presence of 15 microM fatty acid-free albumin and with radioactive fatty acid concentrations of 5-500 nM, esterification into phospholipid was linear with time and platelet concentration and saturable with respect to fatty acid concentration. Two distinct classes of uptake rate were observed. Arachidonate and 5,8,11,14,17-eicosapentaenoate exhibited high affinity, relatively rapid incorporation into platelet phospholipids at pH 6.5: apparent Michaelis constant (Km) = 30 nM, apparent maximum velocity (Vmax) = 28 pmol/min per 10(9) platelets. Two other eicosanoid precursors, 5,8,11-eicosatrienoate and 8,11,14-eicosatrienoate, exhibited the same Vmax, but Km of 85 and 60 nM, respectively. Under the same conditions, stearate, oleate, and linoleate were incorporated into phospholipids much less efficiently (Vmax approximately 8 pmol/10(9) cells per min, apparent Km greater than or equal to 170 nM). Qualitatively similar results were found at pH 7.4. Uptake of radiolabeled, rapid-uptake fatty acids was not diminished by the presence of excess, unlabeled, slow-uptake fatty acids. Thus, the specificity of this esterification system resembles that of the arachidonate-specific, long-chain acyl-CoA synthetase present in platelets. It may represent the expression in vivo of the synthetase, although the apparent affinity of the synthetase for fatty acid is much less. This esterification system probably represents the physiologic mechanism for platelet arachidonate uptake, whereby arachidonate is collected from plasma, despite the fact that its concentration is considerably lower than that of other plasma fatty acids.

8,11,14-Eicosatrienoic Acid↗
PubMed1982

Chain elongation and desaturation of eicosapentaenoate to docosahexaenoate and phospholipid labeling in the rat retina in vivo.

The metabolism of [1-14C]eicosapentaenoic acid in the retina after intravitreal injections in the adult rat eye was studied. The acylation of eicosapentaenoic acid and the appearance of labeled docosapentaenoate and docosahexaenoate in individual phospholipids was observed at 3, 5 and 30 min after injection. The elongation and desaturation products represented about 8 and 4%, respectively, of the total radioactivity of phospholipids 3 min after injection. The highest labeling was found in phosphatidylcholine, phosphatidylinositol and phosphatidic acid. The uneven labeling profiles and the specific activities in individual phospholipids suggested that, in addition to the deacylation-acylation route for the introduction of polyenoic acyl groups into phospholipids, acylation may also take place during the synthesis of phosphatidic acid, followed by channeling to phospholipids.

Animals↗
PubMed1982

Fatty acid specificity in the inhibition of cell proliferation and its relationship to lipid peroxidation and prostaglandin biosynthesis.

Primary cultures of smooth muscle cells were established from the medial layer of guinea pig aorta. Cells at passage level 4 were treated with different series of fatty acids belonging to the n-9, n-6 and n-3 families. Lipid peroxidation was measured by the thiobarbituric acid assay and prostaglandin biosynthesis was measured by the radioimmunoassay of PGE and 6-keto-PGF1 alpha. Cell proliferation was estimated from the total cell number of cultures seeded at low density. 18:1(n-9) did not form lipid peroxides and this fatty acid stimulated cell proliferation. All fatty acids which generated lipid peroxides inhibited cell proliferation, but inhibition was correlated with the degree of lipid peroxidation only in the n-9 fatty acid family. 22:4(n-6) and 22:6(n-3) inhibited prostaglandin biosynthesis. 18:2(n-6), 18:2(n-9), 18:3(n-3), 20:2(n-9), 20:3(n-3) and 20:5(n-3) had no effect on prostaglandin biosynthesis. 18:3(n-6), 20:3(n-6) and 20:4(n-6) generated prostaglandins. 20:3(n-9) generated metabolites with prostaglandin immunoreactivity. The inhibition of cell proliferation did not correlate with enhanced or inhibited prostaglandin synthesis. The inhibition of cell proliferation was related to the structures of the different polyunsaturated fatty acid families decreasing in the order n-9 greater than n-6 greater than n-3. Eicosatrienoic acids were the most effective inhibitors of cell proliferation in each fatty acid family and 20:3(n-9) was the most potent eicosatrienoic acid. These data show that specific as yet unrecognized products of fatty acid metabolism are responsible for the inhibition of cell proliferation.

6-Ketoprostaglandin F1 alpha↗
PubMed1982

Modulation of leukotriene formation by various acetylenic acids.

A series of acetylenic acids varying in chain length as well as in number and position of triple bonds were tested for their effect on arachidonic acid metabolism via cyclo-oxygenase and 5-lipoxygenase in homogenates of RBL-l cells. A number of trends which differentiate 5-lipoxygenase from cyclo-oxygenase were observed: (a) In general, the potency of the acetylenic acids to inhibit 5-lipoxygenase increased with the carbon chain length up to carbons. (b) A minimum of three triple bonds is necessary for the inhibitory action. (c) With the 20-carbon delta 8 and delta 6 acetylenic acids, activity decreased when the number of triple bonds increased from three to four. These structure activity relationships were not observed with cyclo-oxygenase. The delta 4 acetylenic acids proved to be an interesting group of compounds. They did not inhibit cyclo-oxygenase or 5-lipoxygenase but were good inhibitors of SRS synthesis. The potency of the delta 4 acetylenic acids increased with chain length, and 21:4 (4a, 7a, 10a, 13a) was the most potent compound inhibiting SRS formation. The delta 4 acetylenic acids are therefore useful tools for investigating the function and action of LTC4 and LTD4.

Animals↗
PubMed1982

Selective inhibitors of platelet arachidonic acid metabolism: aggregation independent of lipoxygenase.

The use of acetylenic acid analogs differing in chain length or position of the triple bonds permitted the systemic study of structure activity relationships for the arachidonate metabolizing enzymes (i.e, cyclo-oxygenase and lipoxygenase) in platelets and the relationship of these enzymes to aggregation. We were able to demonstrate analogs that were differentially selective in altering platelet arachidonic acid metabolism. We found analogs that preferentially: (a) inhibited cyclo-oxygenase only, (b) inhibited the 12-lipoxygenase only, (c) inhibited the cyclo-oxygenase and lipoxygenase, and (d) inhibited neither enzyme in platelets. There was a direct correlation between the rank order of potency of the acetylenic analogs to inhibit platelet cyclo-oxygenase and to suppress aggregation. Certain structural features of the triynoic acetylenic analogs were critical in influencing platelet function; thus the presence of a triple bond at position 14 as well as the lack of triple bond at position 5 resulted in analogs which inhibited both cyclo-oxygenase and platelet aggregation. On the other hand, analogs that inhibited only platelet 12-lipoxygenase were very weak inhibitors of platelet aggregation. These inhibitors provide potentially powerful tools for dissociating the two arachidonate metabolic pathways. If other tissues are are readily manipulated as platelets, the analogs may be especially useful for gaining insight into the contribution of lipoxygenase products to biological function.

Arachidonate Lipoxygenases↗
PubMed1982

Unidimensional thin-layer chromatography of phospholipids on boric acid-impregnated plates.

A unidimensional thin-layer chromatography system for the separation of phospholipids has been developed. The method employs precoated plates impregnated with boric acid and is capable of resolving eight phospholipid standards, including phosphatidylinositol, phosphatidylserine, and phosphatidylglycerol. Liver, kidney, and platelet phospholipids of the rat were resolved into six major classes using this method. Each was judged to be pure by two-dimensional thin-layer chromatography. The use of boric acid thin-layer chromatography for the separation of phospholipids should find wide application.

Animals↗
PubMed1981

Selective inhibitors of platelet lipoxygenase: 4,7,10,13-eicosatetraynoic acid and 5,8,11,14-henicosatetraynoic acid.

Nine acetylenic acids were evaluated to determine what structural features are required for selective inhibition of platelet lipoxygenase. Both 4,7,10,13-icosatetraynoic acid and 5,8,11,14-henicosatetraynoic acid inhibited the synthesis of 12-L-hydroxy-5,8,10,14-icosatetraenoic acid (HETE) more than 95 percent without significantly altering the production of either thromboxane B2 or 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT). The ID50 concentrations (microM) for inhibiting the synthesis of thromboxane B2 and HETE were respectively 51 and 0.46 with 4,7,10,13-icosatetraynoic acid while similar concentrations of 64 and 0.31 were found for 5,8,11,14-henicosatetraynoic acid.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1981

Inhibition of platelet arachidonic acid 12-lipoxygenase by acetylenic acid compounds.

Eighteen acetylenic fatty acids were tested as inhibitors of human platelet arachidonic acid 12-lipoxygenase. 4,7,10,13-Eicosatetraynoic (4,7,10,13-ETYA) acid emerged as the most potent compound. Additional experiments have shown that 4,7,10,13-ETYA selectively blocked the 12-lipoxygenase in washed human platelets with lesser activity against the cyclooxygenase. The ID50 value for lipoxygenase was 7.8 microM in comparison with an ID50 of 100 microM for the cyclooxygenase. The commonly used inhibitor 5,8,11,14-eicosatetraynoic acid inhibited both enzymes with equal potency. It appears that 4,7,10,13-ETYA may be a valuable lead for selective modulation of the 12-lipoxygenase pathway in platelet or other target tissues.

5,8,11,14-Eicosatetraynoic Acid↗