Repair synthesis of DNA induced by the urinary N-hydroxy metabolites of carcinogenic arylamines in urothelial cells of susceptible species.

Urinary N-hydroxy metabolites of the bladder carcinogens, 2-aminofluorene and 4-aminobiphenyl, were examined for the induction of unscheduled DNA synthesis (UDS) in urothelial cells of several susceptible species. N-Hydroxy-2-aminofluorene, N-hydroxy-2-acetylaminofluorene (N-OH-AAF), N-hydroxy-4-aminobiphenyl, N-hydroxy-4-acetylaminobiphenyl, and the N-glucuronides of these two hydroxylamines induced UDS in the urothelial cells of dogs, rats, and rabbits. N-Hydroxy-2-aminonaphthalene, N-hydroxy-2-acetylaminonaphthalene, and the N-glucuronide of the hydroxylamine were not active. The induction of UDS in dog cells by N-OH-AAF or N-acetoxy-2-acetylaminofluorene, but not by N-hydroxy-2-aminofluorene, was inhibited by paraoxon. The microsomal fraction of dog urothelial cells catalyzed the binding of N-OH-AAF to transfer ribonucleic acid; the enzyme activity was completely inhibited by paraoxon, suggesting that N-deacetylase, but not N-,O-acetyltransferase, was responsible for the binding. The O-glucuronide of N-OH-AAF did not induce UDS in the urothelial cells of dogs, rats, or rabbits, nor did it bind to tRNA in the presence of dog urothelial enzymes, which suggest that N-OH-AAF is detoxified by O-glucuronidation. These results are consistent with the hypothesis that nonacetylated, N-hydroxylated metabolites play a major role in arylamine-induced bladder carcinogenesis. The importance of arylacethydroxamic acid metabolites in bladder carcinogenesis for various species may be inversely related to the rate of hepatic O-glucuronidation.

Optimisation and validation of a HS-SPME-GC-IT/MS method for analysis of carbonyl volatile compounds as biomarkers in human urine: Application in a pilot study to discriminate individuals with smoking habits.

A new and simple analytical approach consisting of an automated headspace solid-phase microextraction (HS-SPME) sampler coupled to gas chromatography-ion trap/mass spectrometry detection (GC-IT/MS) with a prior derivatization step with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was developed to detect volatile carbonyl metabolites with low molecular weights in human urine. A central composite design (CCD) was used to optimise the PFBHA concentration and extraction conditions that affect the efficiency of the SPME procedure. With a sample volume of 1 mL, optimal conditions were achieved by adding 300 mg/L of PFBHA and allowing the sample to equilibrate for 6 min at 62°C and then extracting the samples for 51 min at the same temperature, using a divinylbenzene/polydimethylsiloxane (DVB/PDMS) fibre. The method allowed the simultaneous identification and quantification of 44 carbonyl compounds consisting of aldehydes, dialdehydes, heterocyclic aldehydes and ketones. The method was validated with regards to the linearity, inter- and intra-day precision and accuracy. The detection limits ranged from 0.009 to 0.942 ng/mL, except for 4-hydroxy-2-nonenal (15 ng/mL), and the quantification limits varied from 0.029 to 1.66 ng/mL, except for butanal (2.78 ng/mL), 2-butanone (2.67 ng/mL), 4-heptanone (3.14 ng/mL) and 4-hydroxy-2-nonenal (50.0 ng/mL). The method accuracy was satisfactory, with recoveries ranging from 90 to 107%. The proof of applicability of the methodology was performed in a pilot target analysis of urine samples obtained from 18 healthy smokers and 18 healthy non-smokers (control group). Chemometric supervised analysis was performed using the volatile patterns acquired for these samples and clearly showed the potential of the volatile carbonyl profiles to discriminate urine from smoker and non-smoker subjects. 5-Methyl-2-furfural (p<0.0001), 2-methylpropanal, nonanal and 2-methylbutanal (p<0.05) were identified as potentially useful biomarkers to identify smoking habits.

Epinephrine, norepinephrine, and dopamine during a 4-day head-down bed rest.

Head-down bed rest at an angle of 6 degrees was used as an experimental model to simulate the hemodynamic effects of microgravity, i.e., the shift of fluids from the lower to the upper part of the body. The sympathoadrenal activity during acute (from 0.5 to 10 h) and prolonged (4 days) head-down bed rest was assessed in eight healthy men (24 +/- 1 yr) by measuring epinephrine (E), norepinephrine (NE), dopamine (DA), and methoxylated metabolite levels in their plasma and urine. Catecholamine (CA) and methoxyamine levels were essentially unaltered at any time of bed rest. Maximal changes in plasma were on the second day (D2): NE, 547 +/- 84 vs. 384 +/- 55 pg/ml; DA, 192 +/- 32 vs. 141 +/- 16 pg/ml; NS. After 24 h of bed rest, heart rate decreased from 71 +/- 1 to 63 +/- 3/min (P less than 0.01). Daily dynamic leg exercise [50% maximum O2 uptake (VO2 max)] used as a countermeasure did not alter the pattern of plasma CA during bed rest but resulted in a higher urinary NE excretion during postexercise recovery (+45% on D2; P less than 0.05). The data indicate no evident relationship between sympathoadrenal function and stimulation of cardiopulmonary receptors or neuroendocrine changes induced by central hypervolemia during head-down bed rest.

Derivatization to stabilize some aliphatic primary hydroxylamines for g.l.c. analysis.

By appropriate choice of trimethylsilylating and trifluoroacetylating reagents and organic solvents for extraction, stable derivative of aliphatic primary hydroxylamines metabolites, N-hydroxyphentermine, N-hydroxychlorphentermine, N-hydroxymexiletene, N-hydroxyphenethylamine, N-hydroxyamphetamine, and N-hydroxy-3,4-dimethoxyamphetamine, were obtained and examined by g.l.c. analysis without decomposition and without interference from the parent drug or other metabolic products.

[The biological diagnosis of pheochromocytoma]. / La stratégie du diagnostic biologique du phéochromocytome.

Pheochromocytomas are tumors secreting large amount of catecholamines. Elevation of blood pressure is the classical manifestation but frequently the tumors are silent and they have to be screened systematically. The biological diagnosis is essential to affirm the tumor before any imaging procedure. It needs to select the most sensitive and specific methods. The sensitivity of VMA, urinary catecholamines and plasma catecholamines assays is respectively 70%, 75%, 85%. Determination of methoxyamines in the urine or better in the plasma reaches a sensitivities of 98%. This represents the best tool for the diagnosis of pheochromocytomas. Only renal or heart failure decrease the specificity of the plasma methoxyamines assay.

[Biological diagnosis of pheochromocytoma: impact of technological improvement]. / Le diagnostic biologique du phéochromocytome: l'impact de l'évolution technologique.

Laboratory diagnosis of pheochromocytoma must give evidence of increased catecholamine production. This requires measurement of catecholamines and their metabolites (normetanephrine NMN, metanephrine MN and/or VMA) in urine or in plasma. The various assays can be also performed during dynamic test that stimulate or inhibit catecholamine release. The recent introduction in biochemistry of high performance liquid chromatography coupled to electrochemical detection (HPLC-ED) has greatly reduced drug-induced interference and has therefore narrowed the reference value range. The two groups of compounds that have most benefited from such analytical improvements are urinary metanephrines and VMA. The technical progress has greatly simplified the laboratory diagnosis of pheochromocytoma both by improving the reliability of already available compounds and by favouring the development of news markers. However, the diagnostic sensitivity of the various urinary and plasmatic markers remains very unequal and the diagnosis of pheochromocytoma requires a carefully planned sequence of studies including appropriate biochemical tests able to affirm or to exclude the diagnosis with a high degree of security while reducing the duration and cost of the investigation. Among urinary markers, metanephrines remain the most direct indices of catecholamine hypersecretion and provide the most reliable biochemical indicators of the existence of pheochromocytoma. The diagnostic sensitivity of urinary metanephrines (about 98%) greatly exceeds that of catecholamines and VMA (60-70%). These differences are related to the diversity and specificity of physiological mechanisms involved in the synthesis, the release and inactivation of markers (catecholamines, metanephrines, VMA) and to the variety of clinical presentations and secretory patterns of pheochromocytomas. Considering the practical necessity of simplifying the collection of laboratory samples, use of plasma assays for the diagnosis of pheochromocytoma has become increasingly routine. However, plasma catecholamines--even when assayed during the clonidine suppression test--have not fully lived up to expectations. The diagnostic sensitivity is far better (about 98%) with the recently developed assays of plasma methoxyamines which, owing to their long half-life, provide long-lasting indicators of the catecholamine discharge and are elevated even in tumors without clinical expression. Laboratory diagnosis is relatively easy when the patient bears a large tumor releasing considerable amounts of catecholamines and metabolites; it becomes more challenging in the case of small tumors or of pretumoral hyperplasia in which only the most reliable biochemical markers are able to confirm the diagnosis of pheochromocytoma.

Biosynthetic preparation of the NO-glucosiduronic acid of N-acetyl-N-phenylhydroxylamine.

1. Sodium (N-acetyl-N-phenylhydroxylamine beta-d-glucosid)uronate was isolated from the urine of rabbits receiving N-acetyl-N-phenylhydroxylamine. 2. Its chemical structure was confirmed by the correspondence of the infrared spectrum of its tri-O-acetyl methyl ester derivative with the tri-O-acetyl methyl ester derivative of an authentic specimen prepared by the Koenigs-Knorr synthesis.

A rare fatal case of silicone resin precursor (SH792) poisoning.

A 39-year-old man committed suicide by ingesting a large quantity of SH792. SH792 is a silicone resin precursor used as a hardener for waterproof paints. It is polymerized in water; this process is then followed by the formation of silicone resin and the release of N,N-diethylhydroxylamine. In this decedent, analysis by infrared spectroscopy showed that polymerized silicone resin was present in the stomach contents. The amount of silica in his tissues was within levels seen in control subjects. N,N-diethylhydroxylamine was detected in the urine (0.7 microliters/ml) but not in the stomach contents. The data suggest that SH792 was polymerized in the stomach and the released N,N-diethylhydroxylamine (DEHA) was absorbed into the body. The mechanism of SH792 poisoning is also discussed.

Identification of a hydroxylamine glucuronide metabolite of an oral hypoglycemic agent.

Glucuronides of piperazine hydroxylamines are rarely reported in the literature, and even more rarely are their structures unambiguously identified. One major metabolite was detected by liquid chromatography/mass spectrometry-radioactivity in urine from monkeys treated with the aryl piperazine oral hypoglycemic agent 9-[(1S,2R)-2-fluoro-1-methylpropyl]-2-methoxy-6-(1-piperazinyl) purine hydrochloride (1). The mass spectrum of this metabolite indicated that it was both monooxygenated and glucuronidated on the piperazine ring. Possible structures included the N- or O-glucuronic acid conjugates of a carbinolamine, hydroxylamine, or N-oxide. Treatment with beta-glucuronidase gave a monooxygenated derivative of the parent compound. 1H NMR analysis of either the glucuronic acid conjugate or the monooxygenated product provided insufficient evidence to unambiguously determine their structures. Incubation of 1 with pig liver microsomes resulted in formation of the same monooxygenated derivative derived from beta-glucuronidase treatment of the glucuronide metabolite. This in vitro system was used to generate sufficient material for analysis by 13C NMR, and the metabolite was identified as a hydroxylamine derivative 2. Incubation of the hydroxylamine with monkey liver microsomes and uridine diphospho-5'-glucuronic acid gave the same glucuronic acid conjugate as that observed in monkey urine. 13C NMR analysis of this biosynthetic product led to its unequivocal structure assignment as the O-glucuronic acid conjugate of the hydroxylamine 3.

Pharmacokinetics and biochemical efficacy of idrapril calcium, a novel ACE inhibitor, after multiple oral administration in humans.

The pharmacokinetic profile and biochemical efficacy of idrapril calcium, a novel angiotensin converting enzyme (ACE) inhibitor, were evaluated in healthy volunteers after multiple dosing for 5 days at the doses of 100, 200 and 400 mg twice daily. The study was conducted as a double-blind, cross-over comparison of idrapril calcium against placebo. Plasma concentrations of idrapril were determined by an indirect enzymatic method. Urinary concentrations were measured by reverse phase high performance liquid chromatography (h.p.l.c.). Plasma samples were also analysed for ACE activity. The pharmacokinetics of idrapril calcium did not change significantly between day 1 and day 5. The values of Cmax and AUC were dose-related over the range of doses tested; tmax was 3-4 h and apparent elimination half-life was 1.4-1.6 h. Plasma ACE activity was maximally inhibited (94-96%) at all dose levels and remained more than 80% depressed from 2 to at least 6 h after idrapril calcium. Although the maximum effect was not dose-related, the duration of inhibition showed some dose-dependency, ACE activity returning to 56, 45 and 29% of the basal value 12 h after the 100, 200 and 400 mg doses, respectively. There were no clinically significant adverse events experienced by the volunteers. No dose-related effects on blood pressure or heart rate were observed. There were no changes in clinical pathology tests, urine analyses or electrocardiograms after dosing with idrapril calcium. Idrapril calcium, the prototype of a new class of ACE inhibitors, appears to be well-tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)