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Isolation of 19,20-dehydroprostaglandins E1 and E2 in human seminal fluid and further studies on 18,19-dehydroprostaglandins E1 and E2.

Human seminal fluid was recently found to contain 18,19-dehydroprostaglandins E1 and E2 (E. H. Oliw, H. Sprecher, and M. Hamberg, (1986) J. Biol. Chem. 261, 2675-2683). In the present study, the cis and trans isomers of 18,19-dehydroprostaglandins E1 and E2 were prepared by incubation of microsomes of ram vesicular glands and glutathione with the precursor fatty acids, 8(Z),11(Z),14(Z),18(E/Z)-eicosatetraenoic acids, and 5(Z),8(Z),11(Z),14(Z),18(E/Z)-eicosapentaenoic acids, and used as references to characterize the 18,19-dehydroprostaglandins of human seminal fluid. Based on separation by reversed-phase high-performance liquid chromatography, capillary gas chromatography-mass spectrometry, and ozonolysis of the (-)-menthoxycarbonyl derivatives and on comparison with the authentic compounds, human seminal fluid was found to contain both the cis and trans isomers of 18,19-dehydroprostaglandins E1 and E2. Furthermore, human seminal fluid contained two related compounds, viz. 19,20-dehydroprostaglandins E1 and E2. The structures of these compounds were established by conversion into the corresponding prostaglandin B compounds, by mass spectrometric analysis and by chemical degradation by oxidative ozonolysis, which afforded, inter alia, 2(S)-hydroxy-adipic acid.

Chemical Phenomena↗

On the determination of isozyme levels in preparations containing cytoplasmic and mitochondrial aspartate aminotransferase.

A spectrophotometric assay has been developed for the determination of the content of each isozyme of aspartate transaminase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) in physiological fluids or tissue extracts. The methods relies on the ability of adipate, at low pH and ionic strength to inhibit the cytoplasmic isozyme but not the one from mitochondria. Two assays are necessary, one at pH 8.0 which measures the content of both isozymes and another at low pH which measures primarily the amount of mitochondrial isozyme. Results obtained by this simple procedure match those in which each isozyme is inhibited by its antibody. The validity of the results obtained by the new method was tested at different ratios of cytoplasmic:mitochondrial isozyme and with tissue extracts. Since the amounts of each isozyme determined by radial immunodiffusion match those values gathered by following enzymatic activity, it is concluded that the quantity of each isozyme obtained from its respective catalytic activity must represent the total protein content of each isozyme in a given sample.

Animals↗

Cyanide-insensitive and clofibrate enhanced beta-oxidation of dodecanedioic acid in rat liver. An indication of peroxisomal beta-oxidation of N-dicarboxylic acids.

The beta-oxidation rate of dodecanedioic acid in rat liver homogenates (600 X g supernatant fraction) was determined by simultaneous measurements of the C6-C12-dicarboxylic acids, i.e., adipic, suberic, sebacic and dodecanedioic acids, in relation to time in assays incubated with dodecanedioic acid. Measurements were performed by a combined gas chromatographic-mass spectrometric technique, i.e., selected ion-monitoring. The beta-oxidation rate was registered as the consumption rate of dodecanedioic acid and as the initial rise in the concentrations of C6-C10-dicarboxylic acids. The beta-oxidation rate of C8-C12-dicarboxylic acids was increased many times in homogenates from clofibrate-treated rats. Moreover, it was unexpectedly found that 2.0 mM cyanide was unable to inhibit the beta-oxidation rate of the dicarboxylic acids in vitro, but in fact caused a minor increase in the rate of beta-oxidation in homogenates from both normal and clofibrate-treated rats. It was concluded that the present results strongly indicate the existence of a peroxisomal beta-oxidation of dicarboxylic acids.

Animals↗

The biogenesis of dicarboxylic acid in rats given hypoglycin.

The metabolic origin of dicarboxylic acids which are produced as a result of hypoglycin poisoning (Jamaican vomiting sickness) was investigated. 14C- and 3H-labelled palmitic acid was administered with hypoglycin to rats, and radioactivity was measured in urinary dicarboxylic acids that were isolated by gas-liquid chromatography. Both isotopes were incorporated into adipic and sebacic acids, indicating a precursor-product relationship. Glutaric acid was, essentially, unlabelled. Preferential incorporation of C-16, relative to C-1 of palmitate, while not evident from data for fraction of isotopic dose incorporated, could be deduced by comparing ratios of 14C:3H in precursor with those ratios in products. It thus appears that omega-oxidation of the fatty acid intervenes predominantly at an intermediate stage of chain-shortening, when inhibition of beta-oxidation by hypoglycin becomes more pronounced.

Animals↗

Metabolism of dicarboxylic acids in rat hepatocytes.

[carboxyl-14C]Dodecanedioic acid (DC12) is metabolized in hepatocytes at a rate about two thirds that of [1-14C]palmitate. Shorter dicarboxylates (sebacic (DC10), suberic (DC8), and adipic (DC6) acid) are formed, mainly DC6, less DC8 and only a little DC10. In hepatocytes from clofibrate-treated rats, more polar products account for most of the breakdown products, presumably because the beta-oxidation proceeds all the way to succinate and acetyl-CoA. [carboxyl-14C]Suberic acid (DC8) is oxidized at a rate only one fifth that of dodecanedioic acid. (+)-Decanoylcarnitine inhibits palmitate oxidation but not the oxidation of dodecanedioic acid. At low concentrations of [carboxyl-14C]dodecanedioic acid or of [1-14C]palmitate, acetylsulfanilamide is more efficiently labeled by the former. High concentrations of dodecanedioic acid inhibit palmitate oxidation and the acetylation of sulfanilamide, presumably because their CoA-esters accumulate in the cytosol. These results indicate that medium-chain dicarboxylic acids are beta-oxidized mainly in the peroxisomes.

Acetylation↗

Interaction of progesterone receptor with immobilized adenosine triphosphate.

Affinity chromatography has been used to study the binding of ATP to cyto-plasmic progesterone receptors of hen oviduct. A resin which selectively binds the receptor protein was prepared by linking ATP covalently to Sepharose 4B through a 6-carbon bridge of adipic acid dihydrazide. Receptor bound to the affinity resin was recovered in a single peak upon gradient elution with KCl (0.2-1 M) or ATP (0-0.1 M). While affinity chromatography was normally accomplished using the [3H]progesterone receptor complex, the hormone was not necessary for ATP binding under the conditions employed. The chromatography of crude receptor preparations allowed up to 100-fold purification with greater than 80% recovery of the receptor. The semipurified receptor appeared intact when analysed by sucrose gradient centrifugation, polyacrylamide gel electrophoresis, and DEAE-cellulose chromatography. The latter procedure separated the receptor into two components, A and B, both of which were capable of binding ATP. Although a specific biochemical role of ATP in hormone receptor action has not been demonstrated, the present studies support this possibility and, in addition, offer a convenient and reliable step for the purification of progesterone receptors.

Adenosine Triphosphate↗

D-aminophosphonovalerate is 100-fold more powerful than D-alpha-aminoadipate in blocking N-methylaspartate neurotoxicity.

Here we report that the D-isomers of 2-amino-5-phosphonovalerate (D-APV) and alpha-amino-adipate (D-alpha AA) protect arcuate hypothalamic neurons from the potent excitotoxic activity of N-methylaspartate (NMA). Consistent with evidence that APV is much more powerful than alpha AA in antagonizing the neuroexcitatory activity of NMA, we found D-APV nearly 100 times more powerful than D-alpha AA in preventing NMA from destroying arcuate neurons.

2-Amino-5-phosphonovalerate↗

Purification of gamma-aminobutyric acid (GABA) receptor from rat brain by affinity column chromatography using a new benzodiazepine, 1012-S, as an immobilized ligand.

The purification of gamma-aminobutyric acid (GABA) and benzodiazepine receptors from the rat brain was employed by the affinity column using a new benzodiazepine, 1012-S, as immobilized ligand. The 1012-S has a aliphatic primary amino group and exhibited an extremely high potency for displacing [3H]flunitrazepam binding to solubilized benzodiazepine receptor preparation (IC50 = 6.0 X 10(-11) M). This benzodiazepine affinity gel retained almost all of the solubilized GABA receptors from synaptic membranes applied to the column, and 25.6% of the receptor was eluted bio-specifically following the application of 1 mM 1012-S. The highest purification fold thus obtained was 4576 (specific activity: 0.99 nmol/mg protein). Furthermore, the successive application of 1-2 M NaSCN also resulted the elution of a highly enriched GABA receptor (specific activity: 0.41 nmol/mg protein; purification fold: 1889). SDS-polyacrylamide gel electrophoretic profiles of the bio-specifically eluted fraction with 1012-S showed the existence of two major bands having the molecular weights of approximately 48,500 and 54,500, in which the former band was selectively photoaffinity-labeled with [3H]flunitrazepam. On the other hand, it was found that the non-specifically eluted fraction with NaSCN contained 4 additional minor bands having molecular weights of 41,000 to 51,000. These results indicate that GABA receptor of the rat brain is coupled, at least in part, with benzodiazepine receptor and is readily purified by the use of highly specific benzodiazepine affinity gel, 1012-S-acetamide adipic hydrazide Sepharose 4B. The present results also suggest that the purified GABA/benzodiazepine receptor complex may contain two different kinds of subunits having the molecular weights of 48,000 and 54,500, in which the former subunit may possess benzodiazepine binding sites.

Animals↗

N-methyl D-aspartate acts as an antagonist of the photoreceptor transmitter in the carp retina.

Glutamate, aspartate, and their agonists, kainate, quisqualate, cysteine sulfinate and N-methyl-D-aspartate (NMDA), were applied to the isolated carp retina while recording from horizontal cells. All these agents, except NMDA, depolarized horizontal cells membrane and reduced responses to light, thus mimicking the effect of the endogenous photoreceptor transmitter. Application of NMDA, on the other hand, caused a membrane hyperpolarization of horizontal cells in the dark, an effect different from its depolarizing effect as observed elsewhere in the central nervous system. NMDA also reduced or blocked the light responses of these cells as well as the depolarizing responses to applications of glutamate, aspartate or kainate. Effects of NMDA on the spectral properties of the horizontal cell responses were identical to the effects of the acidic amino acid receptor antagonists alpha-methyl glutamate, and alpha-amino adipate. Thus, NMDA appears to act as a weak antagonist to the photoreceptor transmitter, whose receptors on the horizontal cell membrane interact with a glutamate-like substance but appear atypical of glutamate receptors described elsewhere in the brain.

Animals↗

Anticonvulsant activity of deaminated analogues of glutamic acid diethyl ester (GDEE).

GDEE, a specific but low-potency antagonist of the quisqualate or 'Type 2' excitatory amino acid receptor, blocks seizures induced by homocysteine and quisqualic acid. Deaminated analogues of GDEE were examined for anticonvulsant activity in mice, for the purpose of determining the structural properties of GDEE required for anticonvulsant activity. The deaminated derivative of GDEE, diethyl glutarate (5 carbon chain) inhibited homocysteine thiolactone (HTL)-induced seizures with an ED50 of 533 mg/kg. A similar compound with carbon chain length increased by two (diethyl pimelate; 7 carbons) was less effective. Decreases or further increases in carbon chain length resulted in a nearly complete loss of activity. Dimethyl glutarate (5 carbons) and dimethyl adipate (6 carbons) were similar to diethyl glutarate in potency, blocking HTL-induced seizures with ED50s of about 625 and 540 mg/kg, respectively. Diethyl ethylmalonate, diethyl maleate, and diethyl fumarate were much less effective. Diethyl glutarate, but not diethyl succinate (4 carbons), blocked seizures induced by intracerebral quisqualic acid. None of the agents tested blocked pentylenetetrazole-induced seizures. Thus a number of deaminated structural variants of GDEE have anticonvulsant activity equal to that of GDEE. The amino group of GDEE appears therefore to be irrelevant for its anticonvulsant effect.

Animals↗

Actions of excitatory amino acid acid agonists and antagonists on the primary afferents of the vestibular system of the axolotl (Ambystoma mexicanum).

In order to determine the nature of the transmitter in the synapse between hair cells and primary afferent fibers, both resting and evoked spike activity of vestibular system afferents were recorded. Excitatory amino acid agonists and antagonists were applied by micro perfusion. Excitatory amino acid agonists consistently increased the firing rate of these afferents. The rank order in potencies of the agonists tested was: kainate greater than or equal to quisqualate greater than D-aspartate greater than or equal to L-glutamate greater than or equal to L-aspartate greater than N-methyl D-aspartate. Blockade of synaptic transmission with high-Mg2+ and low-Ca2+ solutions did not seem to affect the responses to the excitatory amino acid agonists indicating their postsynaptic action. Excitatory amino acid antagonists inhibit both resting and physiologically evoked activity. The rank order of inhibitory potency was: kynurenate greater than L-glutamate diethyl ester greater than D,L-2-amino-4-phosphono-butyrate greater than D-alpha-amino adipate greater than D,L-2-amino-5-phosphonovalerate. These findings suggest that an amino acid-related compound may be the transmitter at this synapse. The relative potencies of agonists and antagonists tested provide evidence that the transmitter released from the hair cells' basal pole in the axolotl vestibular system interacts with postsynaptic kainic/quisqualic type receptors.

Action Potentials↗

Pharmacological characterization of voltage-clamped catfish rod horizontal cell responses to kainic acid.

Excitatory amino acid-induced currents were examined in voltage-clamped rod horizontal cells dissociated from the catfish retina. The cells responded to glutamate (GLU) and the GLU analogues kainate (KA), quisqualate (QA), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), while N-methyl-D-aspartate (NMDA) produced inconsistent responses. Of the effective agonists, only KA produced large, concentration-dependent current responses. While QA, AMPA, GLU, and NMDA were poor agonists, these compounds were able to block rod horizontal cell responses to KA. The rank order potency for this inhibition was: QA greater than AMPA greater than or equal to L-GLU much greater than D-GLU = NMDA. Several excitatory amino acid receptor antagonists were also able to inhibit rod horizontal cell responses to KA. The rank order potency for the inhibition by the compounds tested was: kynurenate greater than cis-piperidine-dicarboxylic acid much greater than D,L-alpha-amino-adipate. Comparison of the potency of several ligands to inhibit rod and cone horizontal cell responses to KA suggested similarities in the KA binding sites of both cell types.

Animals↗

Identification of ethylmalonic acid in urine of two patients with the vomitting sickness of Jamaica.

Large amounts of ethylmalonic acid have been identified in urines from two patients with the vomitting sickness of Jamaica. The amounts were 178 and 882 mug per mg creatinine which are 70 and 350 times, respectively, over control values. Other short and medium chain dicarboxylic acids including glutaric and adipic acids and those with eight and ten carbon chain, saturated and cis-unsaturated, were also detected in large quantities as in the case of hypoglycin treated rats; urine. However, the large increase of urinary ethylmalonic acid in these two human cases is in a sharp contrast to the findings in hypoglycin treated rats in which urinary ethylmalonic acid increased only 3 times over control. It appears that ethylmalonic acid is produced in the cases with the vomiting sickness of Jamaica by carboxylation of n-butyryl-CoA which is not oxidized further due to the inhibition by hypoglycin A. In case of hypoglycin-treated rats, n-butyryl-CoA is mainly conjugated with glycine or deacylated to free butyric acid.

Animals↗

Urinary organic acid profiles of Reye's syndrome patients.

The status of mitochondrial functioning in Reye's syndrome was assessed by comparing organic acid profiles from nine pathological urines with those from normal urines. It was found that Reye's syndrome urines have a normal content of succinic, oxaloacetic, aconitic, and citric acids suggesting that the enzymes of the acid cycle are functional. Elevated pyruvate and depressed alpha-ketoglutarate levels were observed. Abnormal urinary constituents detected were salicylic and adipic acids. Presence of the latter indicates that the enzymes of fatty acid beta-oxidation are functional.

Aconitic Acid↗

Organic acid excretion in a patient with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency: facts and artefacts.

The organic acid excretion in a patient with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency is described. In addition to 3-hydroxy-3-methylglutaric, 3-methylglutaconic, 3-methylglutaric and 3-hydroxyisovaleric acids, substantial amounts of glutaric and adipic acids were repeatedly observed. 3-Methylcrotonic acid and possibly one of its isomers was found to be formed artificially from 3-methylglutaconic acid.

Acyl Coenzyme A↗

Aspartate aminotransferase isoenzymes--differential kinetic assay in serum.

The isoenzymes of aspartate transaminase differ in their kinetic properties in that the cytoplasmic isoenzyme is more readily inhibited by adipate and by 2-oxoglutarate (substrate) at low pH. A differential kinetic assay based on this phenomenon has been optimised for use in assays of serum samples. The new method agrees well with an immune absorption procedure. Methods based on chromatographic separation of the isoenzymes fail in the presence of serum.

Adolescent↗

Altered metabolic profiles of valproic acid in a patient with Reye's syndrome.

Urinary valproate metabolite and endogenous organic acid profiles in a 6-yr-old girl with Reye's syndrome were investigated by means of gas chromatography-mass spectrometry. 2-n-Propyl-3-oxovaleric acid, normally the major metabolite of valproate in man, was undetectable, while 2-n-propylglutaric acid, the end product via omega-oxidation was markedly increased. Polyunsaturated valproate was not found. Valproate-glucuronide was still found as the major metabolite. The clinical findings coupled with a greatly increased excretion of lactate and adipate was compatible with Reye's syndrome. Ketone bodies were not detectable. This case study shows that Reye's syndrome causes altered valproate metabolism, consistent with the defective mitochondrial beta-oxidation of medium chain fatty acids, and suggests that valproic acid should not be used in the treatment of seizures in patients with this syndrome.

Biotransformation↗

Urinary C6-C12 dicarboxylic acylcarnitines in Reye's syndrome.

C6-C12 dicarboxylic acylcarnitines have been identified for the first time in urine from a 2-year-old girl presenting with Reye's syndrome. The acylcarnitines were extracted by ion-exchange chromatography and analysed, both underivatised and as methyl esters using high-resolution fast-atom-bombardment mass spectrometry and B/E-linked scanning. The acylcarnitines were quantified by capillary gas chromatography of the acids extracted after hydrolysis of the acylcarnitine esters. Dodecandioylcarnitine was present in the highest concentration (35.9 mmol/mol creatinine) which exceeded the urinary free dodecandioic acid concentration. The adipic, suberic and sebacic acylcarnitine concentrations were less than 10% of the respective free acid concentrations. It is possible that beta-oxidation of dicarboxylic acids is partially inhibited in Reye's syndrome leading to accumulation of precursor dodecandioyl CoA which is metabolised to dodecandioylcarnitine. The accumulation of these metabolic intermediates may be significant in the pathogenesis of Reye's syndrome.

Carnitine↗