Contact sensitivity to urushiol: role of covalent bond formation.
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Animals↗
Biomedical subjects
N Castagnoli
Publications and source records attributed to N Castagnoli.
A murine model system for contact sensitization to poison oak or ivy urushiol components.
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Animals↗
Metabolic formation of iminium species: metabolism of phencyclidine.
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Animals↗
Renal and biliary elimination of vecuronium (ORG NC 45) and pancuronium in rats.
The urinary excretion of ORG NC 45 (Vecuronium) and of pancuronium was studied in unanesthetized rats and the biliary excretion was studied in anesthetized rats. Urine and bile were analyzed for unchanged drug by a new and specific mass spectrometric assay. Pancuronium was eliminated primarily in the urine (85% +/- 6% of the dose in 12 hours), but little ORG NC 45 appeared in the urine (3.5% +/- 1.1% in 12 hours). Biliary excretion accounted for 46% +/- 4% of the ORG NC 45 dose in 7 hours, but only 7.5% +/- 5.3% of an injected dose of pancuronium appeared in the bile. Thus, it appears that ORG NC 45 (a monoquaternary ammonium compound) has a higher biliary clearance than pancuronium (a bisquaternary ammonium compound). The different biodisposition of these two compounds may be due to the greater lipophilicity and concomitant enhanced permeability into the hepatocyte of ORG NC 45. We conclude that in the rat elimination of pancuronium is primarily via the kidney whereas elimination of ORG NC 45 is dependent on nonrenal mechanisms.
Animals↗
Studies on the biotransformation of ketamine. 1-Identification of metabolites produced in vitro from rat liver microsomal preparations.
The in vitro metabolic fate of the anesthetic agent ketamine [(+)2-o-chlorophenyl-2-methylaminocyclohexanone] has been evaluated using microsomal preparations from rat liver. With the aid of a rapid, nonselective metabolite extraction procedure and sample analysis by combined glass capillary gas chromatography low (and high) resolution mass spectrometry, eight metabolites of the drug were identified, six of which have not been reported previously. The novel metabolites were products of alicyclic ring hydroxylation of ketamine and of N-desmethylketamine (norketamine). Semi-quantitative analysis of metabolites produced during microsomal incubation was achieved using glass capillary gas chromatography. The results from this study indicate that 5,6-dehydronorketamine, previously considered to be a major biotransformation product of ketamine in mammalian systems, is almost certainly a methodological artefact.
Animals↗
Regiospecific attack of nitrogen and sulfur nucleophiles on quinones derived from poison oak/ivy catechols (urushiols) and analogues as models for urushiol-protein conjugate formation.
Attempts to characterize potential biologically important covalent interactions between electrophilic quinones derived from catechols present in poison oak/ivy (urushiol) and biomacromolecules have led to the analysis of model reactions involving sulfur and amino nucleophiles with 3-heptadecylbenzoquinone. Characterization of the reaction products indicates that this quinone undergoes regiospecific attack by (S)-N-acetylcysteine at C-6 and by 1-aminopentane at C-5. The red solid obtained with 1-aminopentane proved to be 3-heptadecyl-5-(pentylamino)-1,2-benzoquinone. Analogous aminobenzoquinones were obtained with the quinones derived from the 4- and 6-methyl analogues of 3-pentadecylcatechol. All three adducts absorbed visible light at different wavelengths. When the starting catechols were incubated with human serum albumin almost identical chromophores were formed. These results establish that cathechols responsible for the production of the poison oak/ivy contact dermatitis in humans undergo a sequence of reactions in the presence of human serum albumin that lead to covalent attachment of the catechols to the protein via carbon-nitrogen bonds. Estimations of the extent of this binding indicate that, at least with human serum albumin, the reaction is quantitative.
Catechols↗
Studies on chiral interactions of 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane and the corresponding N-hydroxy metabolites with cytochrome P-450.
The stereoselective pharmacological behavior and metabolism of the potent psychotomimetic amine 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane have led to an investigation of the interactions of the racemic amine, its enantiomers, and the corresponding N-hydroxy metabolites with rabbit liver microsomal cytochrome P-450. An examination of the formation of cytochrome P-450 metabolic intermediate complexes with these species suggests that N-oxidation of the pharmacologically active (R)-amine in inhibited by the S enantiomer. Additionally, metabolic intermediate complex formation [favored by the (R)-amine] appears to be associated with loss of microsomal mixed function N-oxidase activity. The results have led to the prediction that N-hydroxylation of pure (R)-amine may be a qualitatively more important pathway than that observed with racemic amine even though this biotransformation may be suicidal.
DOM 2,5-Dimethoxy-4-Methylamphetamine↗
Trapping of metabolically generated electrophilic species with cyanide ion: metabolism of methapyrilene.
The popular antihistamine methapyrilene [N,N-dimethyl-N'-(2-pyridyl)-N'-(2-thienylmethyl)-1,2-ethanediamine] recently has been shown to be a potent hepatocarcinogen. Metabolic studies with rabbit liver 100000g microsomal preparations have resulted in the partial characterization of the in vitro metabolic profile of methapyrilene. Evidence for the formation of the N-oxide and the three possible carbinolamines resulting from the NADPH-dependent oxidation of the (dimethylamino)ethyl side chain nitrogen and carbon atoms of methapyrilene is presented. Attempts to trap iminium ion intermediates with electrophilic alkylating potential by coincubating methapyrilene with sodium cyanide have led to the isolation of N-(cyanomethyl)normethapyrilene. The possibility of characterizing the iminium ion intermediate that would result from the oxidative deamination of the dimethylamino moiety was precluded by the chemical instability of the corresponding alpha-cyano amine, which undergoes a spontaneous retro-Michael reaction and hydrolysis to the corresponding amide. The results are discussed in terms of the metabolic activation of methapyrilene to potential alkylating species.
Aminopyridines↗
Photoelectron spectra of psychotropic drugs. 6. Relationships between the physical properties and pharmacological actions of amphetamine analogues.
The valence ionization potentials of seven additional members of a series of 2,4,5-trisubstituted amphetamines (1-phenyl-2-aminopropanes) were measured by UV photoelectron spectroscopy. These and previously published data provide experimental measures of the gross electron-donor ability of the aromatic rings of 23 amphetamines. Analogues bearing the 2,5-dimethoxy orientation were found to possess the lowest ionization potentials (IPs); for the analogously X-substituted compounds, the IPs increased in the order of 2,5-(OMe)2-4-X less than 2,4-(OMe)2-5-X less than 4,5-(OMe)2-2-X. Relationships between human psychotomimetic activity (MU), rabbit hyperthermia (SRU), serotonergic receptor affinity (pA2), and charge-transfer complex stabilities (KDNB) were evaluated statistically. A good correlation (r2 = 0.92) was established between the human and rabbit potencies, but poorer correlations were obtained between animal potencies and pA2's (r2 = 0.68-0.69) or KDNB's (r2 = 0.03!). Analysis of the regression relationships between these pharmacological measures and two physical properties, IP and lipid solubility (as modeled by log P), were explored. In general, greater potency is associated with decreasing IP and increasing log P. However, numerous exceptions to single parameter regressions are found. The unusually great potency of the 2,5-(OMe)2-4-X analogues, while qualitatively related to the physical properties, is quantitatively underestimated by these predictors. However, inclusion of a parameter (pi 4) which explicitly acknowledges the type of the 4-substituent leads to much improved correlations. These results support previous suggestions that 4-substituents interact directly with the receptor.
Amphetamines↗
Trapping of metabolically generated electrophilic species with cyanide ion: metabolism of 1-benzylpyrrolidine.
Incubations of 1-benzylpyrrolidine (4) and specifically deuterium-labeled analogues of 4 with rabbit liver microsomal preparations in the presence of cyanide ion have led to the characterization of 1-benzyl-2-cyanopyrrolidine (13), cis- and trans-1-benzyl-2,5-dicyanopyrrolidine (14a and 14b, respectively), and 1-benzyl-5-cyano-2-pyrrolidinone (15). The cyano adducts of the amine are thought to result from nucleophilic attack by cyanide ion on metabolically generated iminium species. The cyanolactam may be produced by mixed function oxidation of the dicyano compounds. Incubations of tritium-labeled 1-benzylpyrrolidine with rabbit liver microsomal preparations led to the reduced nicotinamide adenine dinucleotide phosphate dependent incorporation of the label into the macromolecular fraction isolated from the postincubates. Although the level of incorporation was low compared to the amount of cyano adducts formed, it is comparable to that reported for other metabolically activated cytotoxic agents. Attempts to identify the possible arene oxide rearrangement product 1-(4-hydroxybenzyl)pyrrolidine (24) as a metabolite of 4 were unsuccessful. The results have prompted us to postulate that metabolically generated iminium ions are capable of alkylating nucleophilic functionalities present on microsomal macromolecules.
Animals↗
Synthetic and preliminary hemodynamic and whole animal toxicity studies on (R,S)-, (R)-, and (S)-2-methyl-3-(2,4,5-trihydroxyphenyl)alanine.
The synthesis, resolution, and absolute configuration assignment of 2-methyl-3-(2,4,5-trihydroxphenyl)alanine (6-OH-alpha-Me-Dopa) are reported. Hemodynamic studies in the rat have shown that this structural analogue and potential metabolite of the clinically useful drug (S)-alpha-Me-Dopa possesses weak hypotensive activity which resides in the R enantiomer. LD50 studies in mice have established that 6-OH-alpha-Me-Dopa is over four times more toxic than alpha-Me-Dopa. Chronic exposure to 6-OH-alpha-Me-Dopa leads to renal and hepatic lesions. The case of oxidation of this hydroquinone to the electrophilic quinone species may contribute to its enhanced toxicity compared to alpha-Me-Dopa.
Animals↗
Metabolic oxidation of nicotine to chemically reactive intermediates.
Studies on the metabolism of nicotine by rabbit liver microsomal fractions in the presence of 0.01 M sodium cyanide have led to the characterization of two isomeric cyanonicotine compounds. The locations of the cyano groups were established by GC--EIMS analyses of the deuterium-labeled products obtained from the specifically deuterium-labeled substrates (S)-nicotine-5',5'-d2, (R,S)-nicotine-2',5',5'-d3, and (R,S)-nicotine-N-methyl-d3. One cyano adduct was shown to be 5'-cyanonicotine, a product previously isolated from similar microsomal preparations. The second cyano adduct was shown to be N-cyanomethyl)nornicotine; this structure assignment was confirmed by synthesis. Formation of N-cyanomethyl)nornicotine appears to occur, at least in part, without prior nitrogen--carbon bond cleavage, implicating the in situ generation of the N-methyleniminium species during the course of metabolic oxidative N-demethylation of nicotine.
Animals↗
Chemical and biological studies of 1-(2,5-dihydroxy-4-methylphenyl)-2-aminopropane, an analogue of 6-hydroxydopamine.
Autoxidation of the bis(O-demethyl)-p-hydroquinone metabolite of the psychotomimetic amine 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) at pH 7.4 leads exclusively to a bicyclic imino quinone. This imino quinone is a good alkylating agent, forming covalent adducts via 1,4 addition to thiols. The autoxidation appears to be dependent on trace metal catalysis and is dramatically inhibited by components of the 10000g supernatant fraction of rabbit liver homogenates. Incubation of tritium-labeled hydroquinone with bovine serum albumin under oxidizing conditions leads to significant amounts of nonextractable radioactivity which presumably is dependent on imino quinone alkylation of nucleophilic functionalities present on macromolecules. Incubation of tritium-labeled DOM with rabbit microsomes in the presence of NADPH leads to irreversible binding of the label to macromolecular components of the microsomes. Since this binding is NADPH dependent, it is likely that metabolic conversion of DOM to the hydroquinone is involved. The imino quinone oxidation product is highly lypophilic and is capable of crossing the blood-brain barrier. Intravenous administration of tritium-labeled imino quinone to rats resulted in significant nonextractable radioactivity in brain tissue. These properties of the hydroquinone metabolite parallel those reported for the structurally related sympatholytic compound 6-hydroxydopamine and have led to the hypothesis that the psychotomimetic properties of DOM may be mediated through 6-hydroxydopamine-type interactions of the hydroquinone with important macromolecules in the brain.
DOM 2,5-Dimethoxy-4-Methylamphetamine↗
Synthesis, redox characteristics, and in vitro norepinephrine uptake inhibiting properties of 2-(2-mercapto-4,5-dihydroxyphenyl)ethylamine (6-mercaptodopamine).
In an attempt to further characterize the structural features of 6-hydroxydopamine analogues that are associated with in vivo neuronal degeneration, the synthesis of 6-mercaptodopamine was undertaken. Although reaction conditions leading to the 1,4 addition of thiols to the model quinone 4-methyl-o-benzoquinone were achieved, attempts to obtain 6-thiolated dopamine analogues by this route failed. The synthesis of 6-mercaptodopamine was achieved by the regioselective thiocyanation of O,O-dimethyldopamine, followed by bis-O-demethylation and reductive cleavage of the S-cyano group. Unlike 6-hydroxydopamine, 6-mercaptodopamine was resistant to autoxidation at pH 7.4. Cyclic voltammometric analysis, however, indicated that electrochemically generated oxidation species of 6-mercaptodopamine are unstable and undergo spontaneous reaction, presumably intramolecular cyclization. In vivo tests revealed that 6-mercaptodopamine inhibits the uptake of tritium-labeled norepinephrine by isolated rat heart atria, although to a much lesser extent than 6-hydroxydopamine.
Animals↗
In vitro studies of poison oak immunity. I. In vitro reaction of human lymphocytes to urushiol.
Poison oak, ivy, and sumac dermatitis is a T-cell-mediated reaction against urushiol, the oil found in the leaf of the plants. This hapten is extremely lipophilic and concentrates in cell membranes. A blastogenesis assay employing peripheral blood lymphocytes obtained from humans sensitized to urushiol is described. The reactivity appears 1--3 wk after exposure and persists from 6 wk to 2 mon. The dose-response range is narrow, with inhibition occurring at higher antigen concentrations. Urushiol introduced into the in vitro culture on autologous lymphocytes, erythrocytes and heterologous erythrocytes produces equal results as measured by the optimal urushiol dose, the intensity of reaction, and the frequency of positive reactors. This suggests that the urushiol is passed from introducer to some other presenter cell. Although the blastogenically reactive cell is a T cell, there is also a requirement for an accessory cell, found in the non-T-cell population, for reactivity. Evidence is presented that this cell is a macrophage.
Adolescent↗
In vitro studies of poison oak immunity. II. Effect of urushiol analogues on the human in vitro response.
Studies were performed to ascertain the effect of urushiol analogues on the in vitro lymphocyte blastogenesis elicited by urushiol in peripheral blood lymphocytes taken from individuals sensitized to poison oak or ivy. Urushiol is a mixture of alkylcatechols composed of a catechol ring coupled to mono-, di-, or tri-unsaturated C-15 or C-17 carbon side chains. Each of these two moieties, catechol ring and side chain, was tested for its role in eliciting reactivity. Analogues tested represented the catechol ring (3-methylcatechol), the mono- or di-unsaturated side chain (oleic or linoleic acid), and the saturated side chain coupled to a catechol ring (pentadecylcatechol), a blocked catechol ring (heptadecylveratrole), or a resorcinol (pentadecylresorcinol). Urushiol with a blocked catechol ring (urushiol dimethyl ether) was also included. Of these, only pentadecylcatechol evoked reactivity in sensitized lymphocytes, and this reactivity was only a fraction of that evoked by urushiol. This suggested that the system has some requirement for the side chain, and that the catechol ring is critical for reactivity. This was further investigated by testing the ability of some of these analogues to inhibit urushiol-specific blastogenesis. No inhibition was noted with compounds bearing the saturated side chain with modified ring structures (pentadecylresorcinol and heptadecylveratrole). However, both 3-methylcatechol and pentadecylcatechol (at equimolar concentrations) blocked reactivity. The results of our experiments suggested that although both the side chain and the catechol ring are required for reactivity, the latter is most critical. Unsaturation in the side chain is important for maximal reactivity because the saturated catechols were only partially as active as the urushiol oil. There may be a greater dose requirement for the catechol ring than for the side chain.
Alkenes↗
Nicotine in breast fluid of nonlactating women.
Using a combination of gas chromatography, mass spectrometry, and selected ion recording techniques, we have identified nicotine and its major metabolite, continine, in the breast fluid of nonlactating women smokers. As little as 25 picograms could be measured by using the deuterated variants, [5',5'-2H]nicotine and [3,3-2H]cotinine, both as internal standards and as carriers in an inverse isotope dilution method.
Body Fluids↗
Oxidative and cardiovascular studies on natural and synthetic catecholamines.
The cyclic voltammometric behavior of epinephrine, norepinephrine, dopamine, epinine, alpha-methyldopamine, beta-methyldopamine, beta-methylepinine, and beta-methoxyepinine has been examined in order to evaluate substituent effects on cyclization rates of the electrochemically generated quinones. We observed that alpha and beta substituents caused a modest enhancement of cyclization rates while an N-methyl group dramatically increased cyclization rates. No correlation was observed between calculated amine pKa values, suggesting that differences in cyclization rates between the primary and secondary amine series were due to inherent nucleophilicity, a measure of which would be gas-phase proton affinities. The acute pressor effects of the newly synthesized catecholamines were compared with the native amines.
Animals↗