Determination of N,N-dimethyldodecylamine and N,N-dimethyloctadecylamine in river and sea water using liquid chromatography tandem mass spectrometry

We developed a selective method for determining N,N-dimethyldodecylamine (DMDA) and N,N-dimethyloctadecylamine (DMOA) concentrations in river and sea water samples using liquid chromatography/tandem mass spectrometry (LC/MS/MS). DMDA and DMOA are suspected to be toxic, and DMDA is categorized as a "Class I Designated Chemical Substance" under the "Act on Confirmation, etc. of Release Amounts of Specific Chemical Substances in the Environment and Promotion of Improvements to the Management Thereof" in Japan. The analytes are extracted from a water sample using solid phase extraction and the extract is evaporated and dissolved in 1 mL methanol for LC/MS/MS analysis. We analyzed DMDA and DMOA in real water samples and found that the analyte peaks were resolved effectively. The method detection limits for DMDA and DMOA were 4.7 and 0.80 ng/L, respectively.

Validity of mutagenic activity as an indicator of river water pollution

OBJECTIVES

To investigate if mutagenicity could be expressed by known water pollution indicators, we determined the mutagenic activity of blue rayon extracts from sampled river water with the Ames test utilizing new strains of bacteria, and compared the results with those of known indicators of water pollution.

METHODS

Water samples were collected by the blue rayon adsorption method at sixteen sites in six rivers in the North Kyushu district. The Assay of mutagenicity was carried out using the Ames test. The test strains wereSalmonella typhimurium TA100, YG1024, YG1041 and YG1042. B(a)P, Trp-P-1 and Trp-P-2 were quantified by HPLC. Determinations of SS, BOD, COD, T-N, T-P, DOC, and A(260)/DOC were performed.

RESULTS

The extracts from five sampling sites showed higher mutagenicity toward strain YG1024 with or without S9mix, and the extracts from two of these five sites showed higher mutagenicity toward strain YG1041 with and without S9mix. However, the water pollution indicators did not show specific trends that were consistent with the mutagenic activity.

CONCLUSIONS

Since the mutagenic activity of river water could not be predicted using known water pollution indicators, we recommend that biological examinations such as mutagenicity tests be added to the indicators that are currently in use.

Determination of 4,4'-, 3,4'-, and 2,2'-diaminodiphenylethers in sediment samples from the sea using liquid chromatography-tandem mass spectrometry

A selective method has been developed for determining the concentration of 4,4'-, 3,4'-, and 2,2'-diaminodiphenylethers in sediment samples from the sea, using liquid chromatography/tandem mass spectrometry (LC/MS/MS). 4,4'-diaminodiphenylether is a suspected toxic compound, and categorized as "Class I Designated Chemical Substance" in Japan. We have investigated the levels of 4,4'-diaminodiphenylether in sediments to evaluate long-term water pollution. The methods detection limits for the 4,4'-, 3,4'-, and 2,2'-diaminodiphenylethers were 2.0, 1.7, and 4.8 ng/g-dry, respectively.

Simple and sensitive determination of 2,4-xylenol in surface water samples from river and sea by gas chromatography-mass spectrometry

A simple and selective method was developed for determination of the concentration of 2,4-xylenol in river and sea water samples using gas chromatography/mass spectrometry (GC/MS). Trace amounts of 2,4-xylenol were collected in a Oasis HLB Plus cartridge, eluted with acetonitrile. The method detection limit of 2,4-xylenol was 1.4 ng/L. The trace peaks of 2,4-xylenol were found in water samples from the river and the sea, and the concentrations were all less than 1.4 ng/L. The nine peaks of the 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-xylenol, and o-, m-, p-ethyl phenol that gave the same m/z ratio were separated efficiently.

Mutagenic activity in roadside soils

Mutagenicity of soils sampled at median strips, roadsides and a park neighboring arterial roads in Kurume City was determined by Ames test. Organic extracts of soils were mutagenic in strains TA98, TA100, YG1041 and YG1042 with and without S9mix. No sample showed mutagenic responses in strains YG3003 or YG7108. Extracts from soils of median strips and beside intersections showed higher mutagenicity and concentrations of PAHs and heavy metals than others, and mutagenic activity of soils correlated significantly with concentrations of PAHs and heavy metals. However, PAHs accounted for less than 12% of total mutagenicity in strains TA98 and TA100 of soil extracts. These extracts showed much higher mutagenicity in YG strains than in TA strains. The results indicate that these soils may be polluted with nitroarenes and aromatic amines.

The mutagenicity of amino-derivatives of diphenyl ether herbicides in new Salmonella typhimurium YG tester strains

In this study, we examined the mutagenicity of four diphenyl ether herbicides and their amino derivatives in Salmonella typhimurium TA tester strains and YG tester strains. YG tester strains have been newly developed for sensitive detection of specific chemicals. S. typhimurium YG 1021, YG 1024, YG 1026 and YG 1029 strains are sensitive to mutagenic nitoroarenes and hydroxyamines. S. typhimurium YG 3003 is a strain that is sensitive to some oxidative mutagens. And S. typhimurium YG 7108 is useful for detection of mutagenic alkylating agents. As a result, each amino derivative of diphenyl ether herbicides is more mutagenic than its parent herbicide in S. typhimurium TA and YG tester strains with metabolic activation by S9 mixture. Moreover, S. typhimurium YG tester strains are more useful for highly sensitive detection of mutagens than S. typhimurium TA tester strains. We also examined the production of amino derivatives in a water environment from parent herbicides. It was clear that diphenyl ether herbicides rapidly transform to amino derivatives in a water environment.

Exogenously added alkylmethylglycerophosphocholine and alkylmethylcarbamylglycerophosphocholine accumulate in plasma membranes more than in intracellular membranes of rabbit platelets

We found that extracellular addition of 2% bovine serum albumin (BSA) to a suspension of rabbit platelets after stimulation with platelet-activating factor resulted in a biphasic extraction of [3H]1-O-alkyl-2-O-methyl (or 2-O-methylcarbamyl)-sn-glycero-3-phosphocholine. A fast phase of extraction of the phospholipid probe by BSA was found to be mainly due to removal of the probe remaining in an outer layer of platelet plasma membrane, whereas a second phase of extraction of the probe by BSA was mostly attributed to redistribution of the probe which had been flipped across the plasma membrane. On the basis of analysis of the biphasic extraction by BSA of 1-O-alkyl-2-O-methyl (or methylcarbamyl)-sn-glycero-3-phosphocholine at various times after its addition, we suggested that the radioactive phospholipid accumulated in plasma membrane more than in intracellular membranes of rabbit platelets. In similar experiments with guinea-pig polymorphonuclear leukocytes, we observed a monophasic extraction of 1-O-alkyl-2-O-methyl (or methylcarbamyl)-sn-glycero-3-phosphocholine by BSA, indicating its unidirectional movement across the plasma membrane.

Exogenous phosphatidic acid with saturated short-chain fatty acyl groups induces superoxide anion release from guinea pig peritoneal polymorphonuclear leukocytes by three different mechanisms

Treatment of suspensions of guinea pig peritoneal polymorphonuclear leukocytes (PMN) with four species of phosphatidate (PA) containing short-chain fatty acids induced sustained superoxide anion (O2-) production after a lag time. The rank order of efficiency of these PAs in triggering O2- production was PA8:0 [1,2-dioctanoyl-sn-glycerol-3-phosphate (GP)] > PA10:0 (1,2-didecanoyl-GP) > PA6:0 (1,2-dicaproyl-GP) > > PA12:0 (1,2-dilauroyl-GP). The O2- release from PMN stimulated with PA10:0 or PA12:0, but not with PA6:0 or PA8:0, was lowered by the addition of 1 mM extracellular Ca2+. Studies with various inhibitors showed that the mechanism of multiphasic O2- production induced by PA8:0 depended on its concentration: 1 and 3 microM PA8:0 induced O2- production constantly after a lag time through a protein kinase-dependent mechanism that was inhibited by 100 nM staurosporine. With concentrations of PA of 10 microM or more, an additional mechanism that was independent of protein kinase became operative and predominant over the protein kinase-dependent one. This protein kinase-independent mechanism was inhibited selectively by 80 microM TMB-8. Concentrations of 30, 60 and 100 microM PA first elicited transient O2- production via another protein kinase-dependent mechanism that was more sensitive to H-7 than to staurosporine, and then sustained O2- production, mainly driven by the protein kinase-independent mechanism. Metabolism of exogenously added [14C]PA8:0 in intact PMN was examined in the presence and absence of propranolol. Results suggest that PA itself is more important rather than its degradation products such as diacylglycerol, in inducing O2- production via three different mechanisms described above.

Platelet-activating factor and its structural analogues in the earthworm Eisenia foetida

The earthworm Eisenia foetida was shown to contain large amounts of ether-containing phospholipids such as alkylacylglycerophosphocholine (61.3% of choline glycerophospholipids) and alkenylacylglycerophosphoethanolamine (66.0% of ethanolamine glycerophospholipids). We also found a substantial amount of ether-containing PAF-like lipid in this animal, its level being increased after the animal is injured. We showed evidence that this PAF-like lipid consists of PAF and PAF analogues containing short chain fatty acids other than acetic acid. Notably, a propionic acid-containing species but not PAF itself, is the most predominant species in this animal. We also confirmed that the earthworms contain enzyme activities involved in the synthesis of PAF and short chain fatty acid-containing PAF analogues. Interestingly, the acetyltransferase activity in earthworms is resistant to high concentrations of the substrate lysophospholipid. Thus, both the structure of the PAF-like lipid and the properties of the enzymes involved in the PAF-like lipid metabolism in the earthworms are somewhat different from those in mammalian tissues.

Platelet-activating factor (PAF)-like phospholipids formed during peroxidation of phosphatidylcholines from different foodstuffs

Previously, we reported that induction of peroxidation of synthetic phosphatidylcholines (PCs) containing a polyunsaturated fatty acid by Fe(2+)-EDTA in the presence of ascorbate resulted in the formation of four types of PCs with an sn-2-oxidatively fragmented acyl group, which had platelet-aggregating activity due to interaction with platelet-activating factor (PAF) receptors. These PCs were compounds with a short-chain monocarboxylate, omega-hydroxymonocarboxylate, dicarboxylate, and dicarboxylate semialdehyde residue, respectively. In this study, we investigated the PAF-like lipids formed during peroxidation of PCs from hen egg yolk, salmon roe, sea urchin eggs, and krill in an FeSO4/EDTA/ascorbate system. The platelet-aggregating activities of these oxidized PCs were all inhibited by FR-900452, an antagonist of PAF. The activity of oxidized krill PC, which was equivalent of 89.8 +/- 8.8 pmol 16:0-PAF/mumol of starting PC, was about 5 times those of oxidized PCs from salmon roe and sea urchin eggs, and about 50 times that of oxidized hen egg yolk PC. The PAF-like phospholipids that had different combinations of long-chain alkyl or acyl groups with one of the above four types of short-chain acyl groups were identified by gas chromatography-mass spectrometry. The results indicated that foodstuffs that are rich in 1-O-alkyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine are potential sources of compounds with high PAF-like activity formed by deleterious lipid peroxidation.

Platelet-aggregating effects of platelet-activating factor-like phospholipids formed by oxidation of phosphatidylcholines containing an sn-2-polyunsaturated fatty acyl group

Previously, we reported the formation of four kinds of phosphatidylcholines (PC) with a short-chain monocarboxylate, dicarboxylate, dicarboxylate semialdehyde or omega-hydroxymonocarboxylate group by oxidation of PCs containing polyunsaturated fatty acid (PUFA) in an FeSO4/ascorbate/EDTA system. In this study, we identified these novel phospholipids by GC-MS as oxidation products of two alkyl ether-linked PCs, 1-O-hexadecyl-2-docosahexaenoyl and 1-O-hexadecyl-2-arachidonoyl-sn-glycero-3- phosphocholine (GPC). The sn-2-acyl moieties of oxidatively fragmented PCs derived from PCs containing docosahexaenoate were one methylene unit shorter than those detected as major oxidation products of PCs containing arachidonate. The platelet-aggregations induced by the oxidized PCs were all inhibited by FR-900452, an antagonist of platelet activating factor (PAF). The PAF-like activity of oxidized 1-O-hexadecyl-2-docosahexaenoyl-GPC, which was equivalent of 1372 +/- 262 pmol 16:0-PAF/mumol starting PC, was 5 times that of oxidized 1-O-hexadecyl-2-arachidonoyl-GPC and 150 times that of oxidized 1-palmitoyl-2-docosahexaenoyl-GPC, suggesting that both an sn-1-alkyl ether linkage and an sn-2-acyl group with a short chain length are important structural requirements for induction of platelet aggregation. These possibilities were confirmed by experiments on the platelet-aggregating activities of synthetic PAF-like compounds. Quantitative measurements by GC-MS of PAF-like phospholipids formed by lipid peroxidation and the activities of synthetic PAF-like phospholipids, suggested that the activities of most oxidized PCs containing PUFA were ascribable to those of PCs with an sn-2-short-chain monocarboxylate group.

Formation of platelet-activating factor-like phospholipids by Fe2+/ascorbate/EDTA-induced lipid peroxidation

We have identified novel phospholipids together with platelet-activating factor and its 1-acyl analogues in purified fractions from a bovine brain lipid extract. These novel compounds were phospholipids with an sn-2-short-chain monocarboxylyl, dicarboxylyl or omega-hydroxymonocarboxylyl group. The profiles of these three types of phospholipids suggest that they were formed by lipid peroxidation. To examine this possibility, we peroxidized synthetic phosphatidylcholines (PC) with an sn-2-polyunsaturated fatty acyl group and PC from bovine brain, with Fe2+/ascorbate/EDTA, and analyzed the secondary degradation products retaining a glycerol backbone by fast atom bombardment-mass spectrometry and GC-MS. Results showed the formation of four kinds of PC with a short-chain monocarboxylate, dicarboxylate, dicarboxylate semialdehyde or omega-hydroxymonocarboxylate moiety. The chain lengths of these PC were related to the position of the double bond vicinal to the esterified carbonyl group in the sn-2-long-chain acyl moiety of the parent PC. The molecular heterogeneity of secondary products formed by the oxidative degradation of bovine brain PC resembled those of the unique phospholipids that we previously detected in the fractions with platelet-activating factor-like activity purified from a bovine brain lipid extract, although the former lacked the species with an acetyl group. These results suggest that all the novel phospholipids with a short-chain acyl group in the brain lipid extract except that with an acetyl group were produced by lipid peroxidation.

Possible influence of lysophospholipase on the production of 1-acyl-2-acetylglycerophosphocholine in macrophages

The rate of production of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (acylPAF) was measured in macrophages following the incorporation of [3H]acetate. Upon activation by A23187, guinea pig alveolar macrophages incorporated [3H]acetate into PAF, but a little radioactivity was found in acylPAF. However, labeling of acylPAF and PAF with [3H]acetate was greatly enhanced in A23187-stimulated alveolar macrophages that had been pretreated with phenylmethanesulphonyl fluoride (PMSF). [3H]PAF was predominantly converted to 1-[3H]alkyl-2-acyl glycerophosphocholine, but [14C]acylPAF rapidly hydrolyzed to 14C-labeled free fatty acid by the incubation with lysates prepared from macrophages. The deacetylation of [14C]acylPAF and [3H]PAF by acetylhydrolase and also the hydrolysis of [14C]lysoPC by lysophospholipase were strongly inhibited in macrophages that had been pretreated with PMSF, while PMSF failed to inhibit the activities of acetyltransferase and acyltransferase. The relative proportions of PAF and acylPAF were quite different in different types of cells. In contrast to alveolar macrophages, peritoneal macrophages, neutrophils and spleen cells from guinea pigs incorporated 2-4 times more [3H]acetate into acylPAF than into PAF. The presence of high levels of acylPAF in peritoneal macrophages was confirmed by GLC-MS analysis. The activities of lysophospholipase, acetylhydrolase and acetyltransferase were measured in alveolar and peritoneal macrophages to determine whether the preferential formation of acylPAF as compared to PAF in peritoneal macrophages was due to differences in these activities between alveolar and peritoneal macrophages. The activity of acetylhydrolase of peritoneal macrophages was almost the same as that in alveolar macrophages. The activity of acetyltransferase in peritoneal macrophages was about half of that in alveolar macrophages. However, the activity of lysophospholipase in peritoneal macrophages was one-sixth of that in alveolar macrophages. These results suggest that lysophospholipase is one of the primary factors involved in the control of the production of acylPAF in activated cells, and that it acts by modulating the availability of lysoPC for the synthesis of acylPAF. Furthermore, high levels of activity of lysophospholipase allow the preferential formation of PAF, via the rapid hydrolysis of lysoPC which would act as a competitive inhibitor of the incorporation of acetate into lysoPAF.

Formation of PAF-like compounds by peroxidation of phospholipids from bovine brain

This short review describes the identification by mass spectrometry of phospholipids having an sn-2-short-chain monocarboxylate, dicarboxylate or omega-hydroxycarboxylate group in a fraction with PAF-like activity from a bovine brain lipid extract. The similar molecular heterogeneities of these unique phospholipids suggest that they are formed via a common mechanism, possibly peroxidation of membrane phosphatidylcholines. This possibility is supported by the finding that these PAF-like compounds were actually formed during peroxidation of synthetic phosphatidylcholines induced by Fe2+/ascorbate/EDTA.

Transbilayer movement and metabolic fate of ether-linked phosphatidic acid (1-O-Octadecyl-2-acetyl-sn-glycerol 3-phosphate) in guinea pig peritoneal polymorphonuclear leukocytes

1-O-Octadecyl-2-acetyl-sn-glycerol 3-phosphate (octadecylacetyl-GP) and its deacetylation product were used as a model of phosphatidic acid and its lyso derivatives, respectively. The binding, transbilayer movement, and intermembranous transport, which should be related to its metabolism in guinea pig peritoneal polymorphonuclear leukocytes, were studied. The albumin extraction procedure (Tokumura, A., Tsutsumi, T., Yoshida, J., and Tsukatani, H. (1990) Biochim. Biophys. Acta 1044, 91-100) was used for studying the transbilayer movement of [3H]octadecylacetyl-GP. The binding, translocation, and metabolism of octadecylacetylglycerol, a dephosphorylated product of octadecylacetyl-GP, in polymorphonuclear leukocytes were also investigated for comparison. The translocation of octadecylacetyl-GP was dependent on temperature, but not on its concentration (in the range of 1-100 nM). The rate of translocation of octadecylacetyl-GP was much slower than that of octadecylacetylglycerol. Treatment of polymorphonuclear leukocytes with N-ethylmaleimide did not affect the translocation of octadecylacetyl-GP. These results suggest that the transbilayer movement of octadecylacetyl-GP is driven by a diffusion process, not by a carrier protein. From these findings, the process of translocation of octadecylacetyl-GP is concluded to be a rate-limiting step in its metabolic conversion to triglyceride, phosphatidylethanolamine, and phosphatidylcholine.

Quantitative analysis of platelet-activating factor in rat brain

Age-related decrease of the platelet-activating factor (PAF) content in rat brain was shown by a convenient method consisting of solid extraction of lipids with a Sep-Pak C-18 cartridge, lipid separation by HPLC and bioassay on rabbit platelets. This method was sufficiently sensitive to allow measurement of PAF in a single brain, and the recovery of PAF was quite high throughout the procedure.

Antagonism of platelet-activating factor in isolated rat colon: possible mechanism

The contractions of three different regions of rat colon in response to platelet-activating factor (PAF) were compared. The ascending colon was found to be the most responsive. The slow contraction of the ascending colon induced by PAF was dependent on external Ca2+. CV-3988, a structural analog of PAF, slowly induced irreversible inhibition of PAF-induced contraction, whereas FR-900452, which is structurally unrelated to PAF, caused rapid reversible inhibition of PAF-induced contraction. No inhibitory effects of CV-3988 were observed when the strip was washed with Tyrode's solution containing 1% bovine serum albumin (BSA). The results suggest that PAF and CV-3988 penetrate slowly into the outer half of the lipid bilayer of plasma membranes of cells in isolated rat colon, and then rapidly diffuse laterally to associate firmly with specific binding sites.

Lysophosphatidic acids induce contraction of rat isolated colon by two different mechanisms

Lysophosphatidic acids (1-linoleoyl-, 1-linolenoyl, 1-arachidonoyl- and 1-O-hexadecyl-sn-glycero-3-phosphate) induced rapid contraction of rat isolated colon which was dependent on external Ca2+, 1-linolenoyl-lysophosphatidic acid having the greatest effect. The contraction induced by 1-linolenoyl-lysophosphatidic acid was reduced considerably by nifedipine and verapamil, but not by atropine or indomethacin. Phosphatidic acids with two short-chain acyl groups induced a small, atropine-sensitive contraction at 100 microM, but phosphatidic acids with two long-chain acyl groups were inactive. These results suggest that unlike phosphatidic acids, lysophosphatidic acids act directly on extracellular sites of the plasma membrane of smooth muscle cells in rat colon, mainly through activation of voltage-sensitive Ca2+ channels.

Identification of sn-2-omega-hydroxycarboxylate-containing phospholipids in a lipid extract from bovine brain

Phospholipids having both a long-chain acyl (palmitoyl or stearoyl) and a short-chain hydroxycarboxylyl (C3-C9) residue were identified by GC-MS in a fraction with PAF-like activity from a bovine brain lipid extract. The hydroxyl group in the hydroxycarboxylate residue was determined to be at the omega-position by comparison of the mass spectra of the tert-butyl-dimethylsilyl derivatives of these compounds with those of synthetic hydroxybutyrate-containing phosphatidylcholines. The co-existence of short-chain hydroxycarboxylate-, monocarboxylate- and dicarboxylate-containing phospholipids in the bovine brain lipid extract suggested that these compounds were formed by peroxidation of membrane phospholipids, especially phosphatidylcholines.

Translocation of exogenous platelet-activating factor and its lyso-compound through plasma membranes is a rate-limiting step for their metabolic conversions into alkylacylglycerophosphocholines in rabbit platelets and guinea-pig leukocytes

Platelets and leukocytes are known to degrade platelet-activating factor (PAF), a potential mediator of inflammation, to its lyso-derivative (lyso-PAF) and then convert this to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholines. However, little is known about the mechanism of internalization of PAF and lyso-PAF, which is a prerequisite for their metabolism within the cells. In this work, the internalization of PAF and lyso-PAF by rabbit platelet and guinea-pig leukocyte plasma-membranes were examined by the washing method with bovine serum albumin. The rates of translocation of PAF and lyso-PAF across guinea-pig plasma membranes were significantly higher than those across rabbit platelets. In these cells, the translocation of PAF was found to be accelerated indirectly by activation of PAF receptors by a small portion of added PAF. Results suggest that a temperature-dependent diffusion process is involved in the internalization of these phospholipids. In both rabbit platelets and guinea-pig leukocytes, the translocation of PAF and lyso-PAF through the plasma membranes was shown to be rate-limiting for the metabolic conversion of these compounds to 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine.

Vitamin E. deficiency increases the synthesis of platelet-activating factor (PAF) in rat polymorphonuclear leucocytes

Vitamin E deficiency was found to stimulate FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine)-induced biosynthesis of PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in polymorphonuclear leucocytes (PMN) from rat peritoneum. In three separate experiments each, the amounts of PAF synthesized during 6 min and 12 min incubation of PMN cells from control, vitamin E-supplemented, and vitamin E-deficient rats were 129-240, 131-227 and 248-354 pmol/10(6) cells, respectively. The activity of the acetyl-transferase, which transfers the acetyl moiety of [3H]acetyl-CoA to 2-lysoPAF (1-O-alkyl-sn-glycero-3-phosphocholine) to form [3H]PAF, was higher in PMN homogenates from vitamin E-deficient rats (2.28 +/- 0.07 nmol/min/mg protein) than in those from E-supplemented rats (1.06 +/- 0.10 nmol/min/mg protein). However, there was no difference between the two groups in the activity of acetylhydrolase (4.26 +/- 0.71 and 4.26 +/- 0.06 nmol/min/mg protein, respectively), measured as degradation of [3H]PAF to [3H]lysoPAF. In vitro addition of alpha-tocopherol did not inhibit the increased activity of acetyl-transferase in vitamin E-deficient rats, indicating that the enzyme in vitamin E-supplemented rats was not directly inhibited by alpha-tocopherol. The acetyl-transferases of the two groups showed similar Km values for acetyl-CoA, but different Vmax values (225 microM and 6.4 nmol/min/mg protein in vitamin E-deficient rats, and 216 microM and 3.6 nmol/min/mg protein in vitamin E-supplemented rats), suggesting that the enzyme was not activated but increased in amount in vitamin E deficiency.

Novel molecular analogues of phosphatidylcholines in a lipid extract from bovine brain: 1-long-chain acyl-2-short-chain acyl-sn-glycero-3-phosphocholines

A vasodepressor phospholipid fraction named Depressor-IA from a bovine brain lipid extract was analyzed by capillary gas-liquid chromatography-mass spectrometry as tert-butyldimethylsilyl derivatives after hydrolysis with phospholipase C. Results show that Depressor-IA is a mixture of 3 platelet-activating factors and 17 1-acyl analogues. Three platelet-activating factors having sn-1-O-hexadecyl, octadecyl, and octadecenyl groups were suggested to account for the hypotensive activity of Depressor-IA, although the total amount of 1-acyl analogues of platelet-activating factor was much more than that of platelet-activating factor in the purified Depressor-IA. 1-Long-chain acyl-2-short-chain acyl-glycero-3-phosphocholines identified in Depressor-IA included novel molecular analogues having sn-2-propionyl, acryloyl, butyryl, valeryl, caproyl, and hepatonoyl groups.

Novel phospholipids with aliphatic dicarboxylic acid residues in a lipid extract from bovine brain

A vasodepressor phospholipid fraction purified from a lipid extract of bovine brain was found to contain novel phospholipids with both a long-chain acyl group and an aliphatic dicarboxylic acid residue. This was shown by analyzing the fraction as tert-butyldimethylsilyl derivatives of glyceride by capillary GC-MS after hydrolysis with phospholipase C. Six molecular species with a palmitoyl group and an aliphatic dicarboxylate (chain length C4-C9), and two species with both a stearoyl group and a succinate or glutarate residue were detected.

Study of platelet activating factor and its antagonists on rat colon strip with a new method avoiding tachyphylaxis

Platelet activating factor induced slow, but sustained contraction of isolated rat colon in a dose-dependent manner. The contraction persisted even when the strips were washed several times with Tyrode solution. However, the addition of high concentrations of bovine serum albumin to the washing solution led to the rapid relaxation of the strips to the basal level, possibly by removing platelet activating factor tightly bound to rat colon. These strips then responded normally to a second addition of platelet activating factor. Neither the cholinergic nervous system nor release of histamine, serotonin, prostaglandins or leukotriene D4 were significantly involved in the contraction induced by platelet activating factor. FR-900452 and CV-3988, recently found to be antagonists of platelet activating factor, selectively blocked the contraction of rat colon induced by the active phospholipid, indicating that it induced contraction by a direct stimulatory effect on the smooth muscle of rat colon in a receptor-mediated manner.

The effects of alpha-tocopherol on site-specific lipid peroxidation induced by iron in charged micelles

alpha-Tocopherol inhibited H2O2-Fe2+-induced lipid peroxidation of linoleic acid (LA) by scavenging OH radicals in tetradecyltrimethylammonium bromide (TTAB) micelles. The inhibiting ability of alpha-tocopherol was much greater than that of OH-radical scavengers mannitol and t-butanol. In contrast, alpha-tocopherol enhanced linoleic acid hydroperoxide (LOOH)-Fe2+-induced lipid peroxidation through regeneration of Fe2+ in sodium dodecyl sulfate (SDS) micelles containing LA. alpha-Tocopherol was oxidized by Fenton's reagent (FeSO4 + H2O2) at a higher rate in SDS micelles than in TTAB micelles. The likely oxidants were OH radicals in the former and Fe3+ in the latter. Both reagents formed in the Fenton reaction. Ferrous ion catalyzed in a dose-dependent manner the decomposition of LOOH and conjugated diene compounds in SDS but not in TTAB micelles. alpha-Tocopherol and Fe3+ individually had no effect on the decomposition of LOOH, but together were quite effective. The rate of the decomposition was a function of the concentration of alpha-tocopherol. The mechanism of "site-specific" antioxidant action of alpha-tocopherol in charged micelles is discussed.

Evidence for existence of various homologues and analogues of platelet activating factor in a lipid extract of bovine brain

Vasodepressor phospholipid with platelet-aggregating activity was highly purified from a lipid extract of bovine brain and subjected to field desorption-mass spectrometry. It was further analyzed by gas-liquid chromatography-mass spectrometry after hydrolysis with phospholipase C and conversion to tert-butyldimethylsilyl derivatives. Results indicated the presence of four species of platelet activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) and ten acyl analogues of PAF. The acyl analogues of PAF included species having an sn-2-propionyl or sn-2-butyryl group, which have not been previously detected in natural sources. The total amount of acyl analogues of PAF was much higher than that of PAF.

Platelet aggregation induced by ether-linked phospholipids. 2. Mechanism of desensitization of rabbit platelets by platelet activating factor and reversibility of inhibitory actions of its antagonists

Rabbit platelets pretreated with CV-3988 had reduced responsiveness to platelet activating factor(PAF) even after the platelets had been washed with a buffer. This was due to its tight binding to receptor sites for PAF, but not conformational changes of the receptor, because the platelets that were pretreated with CV-3988 and then washed with buffer containing 0.5% bovine serum albumin showed full responsiveness to PAF. In contrast, the reduced responsiveness of PAF-pretreated rabbit platelets was not reversed by washing with buffer containing 0.5% BSA. The PAF-pretreated platelets showed significantly lower responsiveness to 1-O-hexadecyl-2-O-monomethylaminocarbonyl-sn-glycero-3-phosphochol ine (MC-PAF) than to PAF, although MC-PAF had the same potency as PAF on inducing aggregation of normal rabbit platelets by interacting with receptor sites for PAF. These results suggest that the desensitization is accompanied by a decreased affinity of receptor sites for PAF or reduced efficiency in coupling of activated receptor to regulatory protein in plasma membranes rather than loss of receptor sites.

Platelet aggregation induced by ether-linked phospholipids. 1. Inhibitory actions of bovine serum albumin and structural analogues of platelet activating factor

Ether-linked lysophosphatidic acid was able to induce aggregation of platelets from various animals. Feline platelets were the most sensitive followed in decreasing order by human, bovine and rabbit platelets. ONO-6240 and CV-3988, which are antagonists of platelet activating factor, did not inhibit aggregation of feline platelets induced by ether-linked lysophosphatidic acid, indicating that the aggregation induced by the lysophosphatidic acid did not involve receptors for platelet activating factor. An addition of bovine serum albumin caused dose-dependent inhibitions on the aggregation of platelets by both ether-linked lysophosphatidic acid and platelet activating factor. Moreover, 0.5% bovine serum albumin reversed platelet aggregation by the active phospholipid before this aggregation reached a maximum. These results suggest that the lysophosphatidic acid exerts its stimulatory action extracellularly, probably by interacting with specific sites on the surface of platelet.

A platelet-aggregating and hypotensive phospholipid isolated from bovine brain

A phospholipid that differs from known active lipids and causes potent platelet aggregation and weak hypotension has been isolated from bovine brain. Its platelet aggregating effect on heparinized platelet-rich plasma from rabbits, was at a threshold concentration of about 0.2 nmol ml-1 as phosphorus. The effect was inhibited by CV-3988. The phospholipid was converted by diazomethane treatment to another active lipid that caused short-term hypotension, but not platelet aggregation, rather it inhibited the aggregation of rabbit heparinized platelets induced by platelet-activating factor.

Involvement of lysophospholipase D in the production of lysophosphatidic acid in rat plasma

A vasoactive lipid present in rat plasma that had been incubated at 37 degrees C for 48 h was identified as lysophosphatidic acid with the following fatty acid composition: palmitic acid (25.2%), stearic acid (8.4%), oleic acid (7.0%), linoleic acid (44.4%) and arachidonic acid (11.9%). The involvement of lysophospholipase D in the production of lysophosphatidic acid was suggested on the basis of extensive analyses of phospholipids in the plasma. Results indicated that lysophospholipase D hydrolyzed polyunsaturated lysophosphatidylcholines preferentially to the saturated species. Exogenously added platelet activating factor was found to be first converted to its lyso derivative by an acetylhydrolase in rat plasma and then degraded by lysophospholipase D to 1-alkyllysophosphatidic acid to a similar extent with exogenously added lyso derivative of platelet activating factor; their percent conversions to lysophosphatidic acid were higher than those of saturated 1-acyllysophosphatidylcholines, but lower than those of polyunsaturated 1-acyllysophosphatidylcholines.

Fluorescent pigments by covalent binding of lipid peroxidation by-products to protein and amino acids

The fluorescent products formed on reaction of 12-oxo-cis-9-octadecenoic acid (12-keto-oleic acid) with about 20 different amino acids, polylysine and bovine serum albumin (BSA) were studied. Besides glycine, only the basic amino acids histidine, lysine and arginine gave products with strong fluorescence. N-Acetylation of amino acids greatly reduced the fluorescence of their reaction products. The formation of fluorescent products was inhibited strongly by SH-amino acids such as N-acetyl-cysteine and glutathione. Polyacrylamide gel electrophoresis showed that BSA treated with 12-keto-oleic acid was more acidic than untreated or ricinoleic acid-treated BSA, indicating that basic amino acid residues in BSA were modified by reaction with the keto fatty acid. None of the structural analogs of 12-keto-oleic acid tested--12-oxo-trans-10-octadecenoic acid, 12-oxo-octadecanoic acid, 12-hydroxy-cis-9-octadecenoic acid (ricinoleic acid), cis-9-octadecenoic acid (oleic acid) and linoleic acid--reacted with glycine to give a fluorescent product. The fluorescent products formed on reaction of 12-keto-oleic acid methyl ester with benzyl amine and glycine methyl ester were shown to be 8-(N-substituted-4,5-dihydro-4-oxo-5-hexyl-5-hydroxy-2-pyrrolyl) octanoic acid methyl esters. The fluorescence properties of these compounds were attributed to the chromophobic system NC = CC = O which contains 6 pi electrons. This investigation contributes to insight of the mechanism of formation of fluorescent pigments, probably by a similar reaction of other compounds of the beta, gamma-unsaturated carbonyl type.

The effect of concentration on the antioxidant effectiveness of alpha-tocopherol in lipid peroxidation induced by superoxide free radicals

Egg yolk phosphatidylcholine liposomes were rapidly oxidized in the presence of chelated iron and a superoxide-generating system. alpha-Tocopherol incorporated in the bilayer was oxidized at the same time. No lipid or alpha-tocopherol oxidation occurred in liposomes composed of dimyristoyl phosphatidylcholine. The antioxidant did not inhibit lipid peroxidation until its concentration reached a critical level, which depended on the effectiveness of the oxidative stress. Beyond this level, peroxidation was inhibited completely and, simultaneously, the rate of oxidation of tocopherol was lowered. The results suggest that the antioxidant efficiency of alpha-tocopherol depends on its ability to react mainly with the chain-initiating or chain-propagating lipid radicals. This, in turn, is closely tied to the tocopherol content of the membrane. Ascorbate inhibited the consumption of alpha-tocopherol, possibly by regenerating its reduced form.

Isolation of diosgenin[(25R)-spirost-5-en-3 beta-ol] from a lysate of a new hypotensive phospholipid occurring in bovine brain

Diosgenin[(25R)-spirost-5-en-3 beta-ol] and cholesterol were detected as trimethylsilyl derivatives by gas chromatography-mass spectrometry in an alkaline lysate of a new hypotensive phospholipid from the lipid fraction of bovine brain. These steroids seemed to be present in the hypotensive phospholipid fraction in some bound forms.

Phosphorus-free antihypertensive lipid from dog peritoneal dialysate, Peritoneal Dialysate Depressor-II

A phosphorus-free lipid with a transient antihypertensive effect was found in a dog peritoneal dialysate by a modified procedure. On silicic acid chromatography of the crude extract, a new hypotensive factor and a new hypertensive factor were separated besides the known antihypertensive phospholipid resembling lysolecithin (Peritoneal dialysate depressor-I). The new antihypertensive factor was purified almost completely by gel filtration on a Sephadex LH-20 column, and found to contain no phosphorus. It was tentatively named Peritoneal Dialysate Depressor-II. The main spot detected on preparative thin-layer chromatography by charring with ethanolic sulfuric acid reagent was found to be responsible for the antihypertensive action. This factor caused a sharp decrease in systemic arterial blood pressure of rats, cats and guinea pigs when injected into the femoral vein. There was no significant change in the heart rate during this hypotension. The hypotensive activity was not affected by previous treatment of the rats or guinea pigs with antimuscarinic, antihistaminic, beta-adrenergic-blocking or ganglionic-blocking agents. The antihypertensive effect of the factor was unaffected on rats pretreated with yohimbine, indomethacin or theophylline. In spinal or reserpinized rats, no detectable reduction of the depressor activity was observed. The factor did not affect isolated guinea pig ileum. Its depressor activity was not changed significantly by its treatment with proteases. No prostaglandin E or F series compounds were detected in the preparation by fluorometric assay with 15-hydroxyprostanoate oxido-reductase and resazurin. The hypotensive factor caused no aggregation of cat or rabbit platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of antispasmodic effect of synthetic lysolecithins with various fatty acid moieties on guinea pig ileum

Non-competitive antispasmodic effects of 8 kinds of synthetic L-alpha-lysolecithins (1-O-acyl-2-lyso-sn-glycero-3-phosphocholine, LPC) with various fatty acid moieties were examined upon the spasmodic actions of histamine and acetylcholine on guinea pig ileum. Five-min pretreatment of the gut with the synthetic LPC was required to be effective. With increase of the concentration of a synthetic LPC for pretreatment of the ileum, the slope of the dose-response curve of histamine or acetylcholine added cumulatively became more gentle, the maximal contraction was suppressed apparently, and which were associated with the shift of the curve to the higher concentration of the stimulants. Of LPCs with saturated fatty acid palmitoyl-LPC showed the strongest effect, followed by myristoyl-, stearoyl-, lauroyl- and decanoyl-LPCs in order. Incorporation of cis-double bond into the C18 fatty acid chain of LPC resulted in slight decrease of the antispasmodic effect. The relaxating effect of LPCs on perfused rabbit ear vessel preparations was similar in order.

Analyses of lysophosphatidic acids by gas chromatography mass spectrometry without hydrolytic pretreatment

Lysophosphatidic acids having different fatty acyl moieties were directly analysed by gas chromatography/mass spectrometry after silylation. Trimethylsilyl derivatives of various LPAs escaped thermal degradation, and electron impact and chemical ionization of these derivatives yielded many ions which were useful for the structural determination. It was found by this new method that five species of lysophosphatidic acids were formed in rat plasma during incubation at 37 degrees C.

Contractile effect of 1-O-hexadecyl-2-O-acetyl-sn-glycero-3-phosphocholine on strips of isolated rat intestine

The contractile effects of AGEPC were examined on various regions of rat isolated intestine. The duodenum, jejunum and ileum showed only the tonic component of contraction to AGEPC at the low dose (less than 10(-9) M) but at the high dose (10(-7) M) biphasic contractions were induced, consisting of a phasic followed by a tonic component. In the colon, however, the AGEPC-induced maximum contraction was comparable in magnitude to that produced by acetylcholine; also the contraction profile was different from that elicited from the other regions of the intestine. Low doses of AGEPC caused a slow, sustained contraction and at high doses phasic and tonic components were not dissociated.

Biphasic action of platelet-activating factor on isolated guinea-pig ileum

1-0-Hexadecyl-2-0-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) at 10(-10)-10(-9) M induced slow contraction of isolated guinea-pig ileal muscles and the contraction persisted for a long time. At a higher concentration of 10(-7) M, this phospholipid induced more rapid, but not greater, contraction. At higher concentrations (10(-6)-10(-5) M), this phospholipid induced a biphasic response: rapid contraction followed by relaxation. At high concentrations, this compound inhibited acetyl-choline-induced contractions. The stimulatory effect of this phospholipid was ca. 300 times that of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine, while its inhibitory potency on induced contraction was similar to those of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine and its lyso derivative. It was suggested that the differences in effects on contraction of different concentrations of 1-0-hexadecyl- and 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine were due to the effects of these compounds on the ileum: a strong stimulatory effect and a moderate inhibitory effect on contraction.

Contractile actions of lysophosphatidic acids with a chemically-defined fatty acyl group on longitudinal muscle from guinea-pig ileum

Various lysophosphatidic acids caused phasic contractions of longitudinal muscle from guinea-pig ileum, followed by rhythmical contractions of lower magnitude. Polyunsaturated lysophosphatidic acids were more potent than saturated lysophosphatidic acids. Among the lysophosphatidic acids tested, linolenoyl-lysophosphatidic acid was the most active, but its activity was about 3-5 times less than that of prostaglandin F2 alpha. Contractile responses to various lysophosphatidic acids, were partially suppressed by tetrodotoxin, atropine and chlorpheniramine. In addition, lysophosphatidic acid-induced contractions were considerably reduced by pretreatment of the muscle with indomethacin.

Antioxidant activities of tocopherols on Fe2+-ascorbate-induced lipid peroxidation in lecithin liposomes

The antioxidant activities of 4 tocopherols, tocol, and a water-soluble model analog of alpha-tocopherol were compared. Egg lecithin liposomes were used and oxidation was catalyzed by Fe2+-ascorbate. The activities decreased in the order alpha greater than beta greater than gamma greater than delta-tocopherol greater than tocol, in agreement with their potencies in vivo. The water-soluble analog was the least effective. Activity depended on the molar ratio of antioxidant to unsaturated lipid, with one molecule each of the alpha-, beta-, gamma-, delta-tocopherol and tocol capable of protecting, respectively, 220, 120, 100, 30 and 20 molecules of polyunsaturated fatty acid. The mechanism of possible antioxidant effect of the compounds used is discussed.

Cardiovascular effects of lysophosphatidic acid and its structural analogs in rats

Injection of lysophosphatidic acid into anesthetized rats induced immediate hypertension, the effect depending on the structure of the sn-1-acyl moiety of the molecule. A hydroxyl group at the sn-2-position was not necessary, but a wedgeshaped structure was suitable for hypertensive activity. Most lysophospholipids with a chemical group attached to the phosphate portion had only weak hypotensive effects, but the sn-2-acetylated analogs of these depressor lysophospholipids elicited a hypotension at much lower doses. The durations of the hypotensions evoked by the sn-2-acetylated choline phospholipids were longer than those produced by 1-palmitoyl-2-acetoyl-sn-glycerol-3-phosphorylmethanol, ethanol and propanol.