A Novel Approach to Integrate Human Biomonitoring Data with Model Predicted Dietary Exposures: A Crop Protection Chemical Case Study Using Lambda-Cyhalothrin

The appropriate use of human biomonitoring data to model population chemical exposures is challenging, especially for rapidly metabolized chemicals, such as agricultural chemicals. The objective of this study is to demonstrate a novel approach integrating model predicted dietary exposures and biomonitoring data to potentially inform regulatory risk assessments. We use lambda-cyhalothrin as a case study, and for the same representative U.S. population in the National Health and Nutrition Examination Survey (NHANES), an integrated exposure and pharmacokinetic model predicted exposures are calibrated to measurements of the urinary metabolite 3-phenoxybenzoic acid (3PBA), using an approximate Bayesian computing (ABC) methodology. We demonstrate that the correlation between modeled urinary 3PBA and the NHANES 3PBA measurements more than doubled as ABC thresholding narrowed the acceptable tolerance range for predicted versus observed urinary measurements. The median predicted urinary concentrations were closer to the median measured value using ABC than using current regulatory Monte Carlo methods.

Voltammetric measurement of entacapone in the presence of other medicines against Parkinson's disease by a screen-printed electrode modified with sulfur-tin oxide nanoparticles

A screen-printed electrode (SPE) is described modified with sulfur-tin oxide nanoparticles (S@SnO₂NP) for the determination of entacapone (ENT) in the presence of other medicines against Parkinson's disease (PD). The S@SnO₂NP was synthesized through the hydrothermal method and used in the modification of the SPE. The smart utilization of the S@SnO₂NP and the SPE provided excellent properties such as high surface area and current density amplification by embedding an efficient sensing interface for highly selective electrochemical measurement. Under optimized experimental conditions, the anodic peak current related to the ENT oxidation onto the sensor surface at 0.46 V presented a linear response towards different ENT concentration sin the range 100 nM to 75 μM. The limit of detection (LOD) and electrochemical sensitivity were estimated to be 0.010 μM and 2.27 μA·μM^-1·cm^-2, respectively. The applicability of the sensor was evaluated during ENT determination in the presence of other conventional medicines againts, including levodopa (LD), carbidopa (CD), and pramipexole (PPX). The results of the analysis of human urine and pharmaceutical formulation as real samples using the developed sensor were in good agreement withre sults of high-performance liquid chromatography (HPLC) as a standard method. These findings demonstrated that the strategy based on the SPE is a cost-effective platform creating a promising candidate for practical determination of ENT in routine clinical testing.Graphical abstract.

[Determination of deltamethrin and its toxicity biomarkers in rabbit urine by high performance liquid chromatography-tandem mass spectrometry]

A method was developed for the determination of biomarkers related to toxicity of deltamethrin in rabbit urine by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The target analytes in this method are as follows:deltamethrin and its two metabolites (1R-cis)-3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane carboxylic acid (dibromochrysanthemic acid) and 3-phenoxybenzoic acid (3-PBA), and five toxic biomarkers, viz. serotonin hydrochloride (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), 3-nitropropionic acid (3-NPA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), and 6-methoxyguanine. Urine samples were cleaned by matrix solid-phase dispersion extraction (MSPD) with diatomite; and protein was precipitated with trichloroacetic acid; and then the sample solutions were purified with hydrophilic-lipophilic balance (HLB) solid-phase extraction cartridges. The biomarkers were analyzed with electrospray ionization (ESI) in a positive and negative switching scan mode, in which the positive scan mode was used for deltamethrin, 5-HT, 5-HIAA, 8-OHdG, and 6-methoxyguanine, and the negative scan mode was used for (1R-cis)-3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane, 3-PBA, and 3-NPA. The target compounds were quantified with the external standard using matrix calibration curves. The linear regression curves of the eight target compounds were linear with correlation coefficients no less than 0.9914. The LOD and LOQ of 5-HIAA were 20 μg/L and 50 μg/L, respectively, and the LODs and LOQs of the other analytes were 0.2-5.0 μg/L and 0.5-10 μg/L, respectively. The average recoveries of the analytes spiked in rabbit urine ranged from 74.2% to 98.7% at three levels, with relative standard deviations (RSDs) no more than 12%. The method was simple, fast, accurate, sensitive, and suitable for the detection for the exposure evaluation of deltamethrin.

In vivo dermal absorption of pyrethroid pesticides in the rat

Exposure to pyrethroid pesticides is a potential cause for concern. The objective of this study was to examine the in vivo dermal absorption of bifenthrin, deltamethrin, and permethrin in the rat. Dorsal hair on adult male Long-Evans rats was removed. The next day, the skin was dosed with 1750 nmol (312.5 nmol/cm(2)) of radiolabeled (5 µCi) bifenthrin, deltamethrin, or permethrin in acetone. A nonoccluding plastic cover was glued over the dosing site. The animals were placed in metabolism cages to collect excreta. At 24 h postdosing, the skin was washed with soap and water, and rats in one group were euthanized and their tissues were collected. The skin was removed and tape stripped. The remaining animals were returned to the metabolism cages after the wash for 4 d. These rats were then euthanized and handled as already described. Excreta, wash, tape strips, tissues, and carcass were analyzed for pyrethroid-derived radioactivity. The wash and tape strips removed >50% of the dose and skin retained 9-24%. Cumulative radioactivity in excreta was 0.5-7% at 24 h and 3-26% at 120 h. Radioactivity in tissues was <0.3% of the dose, while carcass retained 2 to 5%. Assuming absorption equals cumulative recovery in skin (washed and tape stripped), excreta, tissues, and carcass, absorption was permethrin ~ bifenthrin > deltamethrin at 24 h and permethrin > deltamethrin > bifenthrin at 120 h. Using the parallelogram approach with published in vitro data, human dermal absorption of these pyrethroids was estimated to be <10% of the dose.

Pesticide exposures to migrant farmworkers in Eastern NC: detection of metabolites in farmworker urine associated with housing violations and camp characteristics

BACKGROUND

The purpose of this paper is to present and evaluate descriptively bivariate associations between urinary metabolites of pesticides and herbicides and migrant camp conditions, violations, and personal worker behaviors at home for farmworkers who do not apply pesticides.

METHODS

We studied 183 migrant farmworker camps in eastern North Carolina in 2010. Data and urine samples were collected from 371 men. Predictor measures included violations in six domains of housing regulations and nonviolation characteristics and personal behaviors that might impact urinary metabolites.

RESULTS

Cockroaches and bathroom violations were predictive of increased exposure to pyrethroids and cyfluthrin/chlorpyrifos, respectively. Changing and storing clothing and shoes in sleeping rooms increased the number of detects for the diazinon metabolite.

CONCLUSIONS

Farmworkers had exposures to multiple chemicals. No single housing domain was identified as critical to mitigating housing-related exposure; specific attention should be paid to changing and storing soiled clothing in sleeping rooms, and insect infestations.

Monitoring phosphodiesterase-4 inhibitors using liquid chromatography/(tandem) mass spectrometry in sports drug testing

RATIONALE

The recent discovery of resveratrol's capability to inhibit cAMP-specific phosphodiesterases (PDEs) and, as a consequence, to enhance particularly the activity of Sirt1 in animal models has reinforced the interest of preventive doping research organizations, especially in PDE4 inhibitors. Among these, the archetypical PDE4-inhibitor rolipram significantly increased the number of mitochondria in laboratory rodents, which further demonstrated a performance increase in a treadmill-test (time-to-exhaustion) of approximately 40%. Besides rolipram, a variety of new PDE4-inhibiting substances including cilomilast, roflumilast, and numerous additional new drug entities were described, with roflumilast being the first-in-class having received clinical approval for the treatment of chronic obstructive pulmonary disease (COPD). Due to the availability of these substances, and the fact that a misuse of such compounds in sport cannot be excluded, it deems relevant to probe for the prevalence of these compounds in sports drug testing programs.

METHODS

Known urinary phase-I metabolites of rolipram, roflumilast, and cilomilast were generated by in vitro incubations employing human liver microsomal preparations. The metabolites obtained were studied by liquid chromatography with high-resolution/high-accuracy tandem mass spectrometry (LC/MS/MS) and the reference product ion mass spectra of established and most relevant metabolites were utilized to provide the information necessary for comprehensive doping controls. The analytical procedure was based on conventional routine doping control assays employing enzymatic hydrolysis followed by liquid-liquid extraction and subsequent LC/MS/MS measurement.

RESULTS

Structures of diagnostic product ions and dissociation pathways of target analytes were elucidated, providing the information required for implementation into an existing test method for routine sports drug testing. The established method allowed for detection limits for the intact drugs of 1-5 ng/mL, and further assay characteristics (intraday precision 1.5-13.7%, interday precision 7.3-18.6%, recovery 20-100%, ion suppression/enhancement, and specificity) were determined. In addition, proof-of-concept analyses concerning roflumilast were conducted with a urine sample obtained from a COPD patient under roflumilast treatment.

Role of PPAR-γ on the pathogenesis and vascular changes in glycerol-induced acute renal failure

Peroxisome proliferator activated receptor-gamma (PPAR-gamma), a nuclear transcription factor, modulates angiotensin II (AII) or thromboxane A(2) (TxA(2)) response in the vasculature via transcriptional regulation of their gene or receptor expression. Increased AII or TxA(2) vasoconstriction and deteriorating renal function observed in glycerol-induced acute renal failure (ARF) may be attributed to a down-regulated PPAR-gamma expression/activity probably via an increased free radical generation. In this study, we investigated the effect of PPAR-gamma induction in glycerol-induced ARF by examining renal vascular reactivity to AII and TxA(2) and by renal expression/activity of PPAR-gamma. Vascular responses to AII or U46619, a TxA(2) mimetic were determined in rat isolated perfused kidney following induction of ARF with glycerol (50%, v/v, i.m.). Extent of renal damage and function were assessed with or without pre-treatment with ciglitazone (9 nmol kg(-1) x 21 days), a PPAR-gamma inducer. In ARF, vasoconstriction was enhanced to AII (three-fold; p<0.05) and U46619 (82%; p<0.05). Ciglitazone reduced AII and U46619 vasoconstriction by 59+/-1% (p<0.05) and 56+/-1% (p<0.05), respectively. Ciglitazone reduced proteinuria (38+/-3%) which was two-fold higher in ARF. Similarly, ciglitazone enhanced Na(+) excretion by 1.5 times while reducing BUN by 49+/-6%. On the contrary, ciglitazone did not change plasma creatinine which was significantly higher in ARF rats. Ciglitazone reduced free radical generation by 30+/-3% while elevating nitrite excretion approximately 2-fold. PPAR-gamma expression and activity were significantly lower in ARF rats and ciglitazone enhanced PPAR-gamma protein expression and activity by 45+/-3% and 52+/-4%, respectively. Data from this study suggest that reduced PPAR-gamma expression and activity may be involved in the pathology of glycerol-induced ARF and induction of PPAR-gamma by ciglitazone confers protection through reduced AII and TxA(2) vasoconstriction and/or enhanced renal function via reducing free radical generation.

Metabolic Profile of FYX-051 (4-(5-Pyridin-4-yl-1H-[1,2,4]triazol-3-yl)pyridine-2-carbonitrile) in the Rat, Dog, Monkey, and Human: Identification of N-Glucuronides and N-Glucosides

FYX-051, 4-(5-pyridin-4-yl-1H-[1,2,4]triazol-3-yl)pyridine-2-carbonitrile, is a novel xanthine oxidoreductase inhibitor that can be used for the treatment of gout and hyperuricemia. We examined the metabolism of FYX-051 in rats, dogs, monkeys, and human volunteers after the p.o. administration of this inhibitor. The main metabolites in urine were pyridine N-oxide in rats, triazole N-glucoside in dogs, and triazole N-glucuronide in monkeys and humans, respectively. Furthermore, N-glucuronidation and N-glucosidation were characterized by two types of conjugation: triazole N(1)- and N(2)-glucuronidation and N(1)- and N(2)-glucosidation, respectively. N(1)- and N(2)-glucuronidation was observed in each species, whereas N(1)- and N(2)-glucosidation was mainly observed in dogs. With regard to the position of conjugation, N(1)-conjugation was predominant; this resulted in a considerably higher amount of N(1)-conjugate in each species than N(2)-conjugate. The present results indicate that the conjugation reaction observed in FYX-051 metabolism is unique, i.e., N-glucuronidation and N-glucosidation occur at the same position of the triazole ring, resulting in the generation of four different conjugates in mammals. In addition, a urinary profile of FYX-051 metabolites in monkeys and humans was relatively similar; triazole N-glucuronides were mainly excreted in urine.

Metabolism of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and its isomer, N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), in rats. 1. Identification of metabolites in feces and urine

Rats were orally dosed with a 1:1 diastereomixture of N-[(R)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (Delaus, S-2900) and N-[(S)-1-(2,4-dichlorophenyl)ethyl]-2-cyano-3,3-dimethylbutanamide (S-2900S), both labeled with 14C, at 200 mg/kg/day for 5 consecutive days, and 16 metabolites in urine and feces were purified by a combination of several chromatographic techniques. The chemical structures of all isolated metabolites were identified by spectroanalyses (NMR and MS). Several of them were unique decyanated and/or cyclic compounds (lactone, imide, cyclic amide, cyclic imino ether forms). Major biotransformation reactions of the mixture of S-2900 and S-2900S in rats are proposed on the basis of the metabolites identified in this study.

Identification of the aromatase inhibitors anastrozole and exemestane in human urine using liquid chromatography/tandem mass spectrometry

Anastrozole (2,2'-[5-(1H-1,2,4-triazol-1-ylmethyl)-1.3-phenylene]bis(2-methylpropionitrile)) and exemestane (6-methylenandrostan-1,4-diene-3,17-dione) are therapeutically used to treat hormone-sensitive breast cancer in postmenopausal women. For doping purposes they may be used to counteract adverse effects of an extensive abuse of anabolic androgenic steroids (gynaecomastia) and to increase plasma testosterone concentrations. Excretion study urine samples and spot urine samples from women suffering from metastatic breast cancer, being treated with anastrozole or exemestane, were collected and analyzed to develop/optimize a detection system for anastrozole and exemestane to allow the identification of athletes who do not comply with the internationally prohibited use of these cancer drugs. The assay was based on liquid-liquid extraction after enzymatic hydrolysis following liquid chromatography/tandem mass spectrometry (LC/MS/MS). Anastrozole, exemestane and its main metabolite (17-dihydroexemestane) were identified in urine by comparison of mass spectra and retention times with respective reference substances. An assay validation for the analysis of anastrozole and exemestane was performed regarding lower limits of detection (anastrozole: 0.02 ng/mL; exemestane: 3.1 ng/mL; dihydroexemestane: 0.5 ng/mL), interday precisions (6.6-11.1%, 4.9-9.1% and 5.6-8.3% for low [10 ng/mL], medium [50 ng/mL] and high [100 ng/mL] concentration) and recoveries (ranged from 85-97%).

Stereoselective pharmacokinetics of RS-8359, a selective and reversible MAO-A inhibitor, by species-dependent drug-metabolizing enzymes

RS-8359, (+/-)-4-(4-cyanoanilino)-5,6-dihydro-7-hydroxy-7H-cyclopenta[d]pyrimidine selectively and reversibly inhibits monoamine oxidase A (MAO-A). After oral administration of rac-RS-8359 to rats, mice, dogs, monkeys, and humans, plasma concentrations of the (R)-enantiomer were greatly higher than were those of the (S)-enantiomer in all species studied. The AUC((R)) to AUC((S)) ratios were 2.6 in rats, 3.8 in mice, 31 in dogs, and 238 in monkeys, and the (S)-enantiomer was almost negligible in human plasma. After intravenous administration of RS-8359 enantiomers to rats, the pharmacokinetic parameters showed that the (S)-enantiomer had a 2.7-fold greater total clearance (CL(t)) and a 70% shorter half-life (t(1/2)) than those for the (R)-enantiomer but had no difference in distribution volume (V(d)). No significant difference in the intestinal absorption rate was observed. The principal metabolites were the 2-keto form, possibly produced by aldehyde oxidase, the cis-diol form, and the 2-keto-cis-diol form produced by cytochrome P450 in rats, the cis-diol form in mice, RS-8359 glucuronide in dogs, and the 2-keto form in monkeys and humans. Thus, the rapid disappearance of the (S)-enantiomer from the plasma was thought to be due to the rapid metabolism of the (S)-enantiomer by different drug-metabolizing enzymes, depending on species.

Identification of the aromatase inhibitor letrozole in urine by gas chromatography/mass spectrometry

Letrozole (1-(bis-(4-cyanophenyl)methyl)-1,2,4-triazole) is used therapeutically as a non-steroidal aromatase inhibitor (Femara) to treat hormone-sensitive breast cancer in postmenopausal women. For doping purposes it may be used to counteract the adverse effects of an extensive abuse of anabolic androgenic steroids (gynaecomastia) and to increase the testosterone concentration by stimulation of the testosterone biosynthesis. The use of aromatase inhibitors has been prohibited by IOC/WADA regulations for male and female athletes since September 2001 and January 2005, respectively. Spot urine samples from women suffering from metastatic breast cancer and being treated with letrozole were collected and analysed to develop/optimise the detection system for metabolites of letrozole to allow the identification of athletes who do not comply with the internationally prohibited use of this cancer drug. The assay was based on gas chromatography/mass spectrometry (GC/MS) and the main metabolite of letrozole (bis-4-cyanophenylmethanol) was identified by comparison of its mass spectrum and retention time with that of a bis-4-cyanophenylmethanol reference. The full-scan spectrum, diagnostic ions and a validation of the method for the analysis of bis-4-cyanophenylmethanol are presented.

Exposure of ground-rig applicators to the herbicide bromoxynil applied as a 1:1 mixture of butyrate and octanoate

Bromoxynil is a herbicide used extensively on the Canadian prairies for weed control in cereal production. This is a report on exposure to and absorption of bromoxynil by farmers during handling, transferring, mixing, and then applying the herbicide to cereal crops using tractor-drawn ground-rigs. The 14 individual spray operations, in which farmers applied 9 kg of bromoxynil (phenol equivalent, p.e.) to 32 ha, lasted from 113 to 549 min and involved one to five tank fills. In five of the spray operations, the farmers wore neoprene gauntlet-style protective gloves. Tractors, equipped with cabs, were used in nine spray operations.Air sampling, hand washes, and dermal patch dosimeters served as the basis to calculate the amount of bromoxynil (p.e.) available for inhalation, deposition on the hands, and deposition under a standardized set of protective clothing. Tractors, equipped with cabs, decreased inhalation exposure by a factor of approximately 10. Use of gauntlet-style neoprene protective gloves decreased dermal exposure to the hands region of the body by 25 times, whereas two layers of laundered cotton provided a protective effect of > 15 in the chest region. The median value for the amount of bromoxynil (p.e.) inhaled was 0.018 microg x kg BW(-1)x kg (p.e.)(-1) for the 14 spray operations. The hands region of the body was the area most exposed to bromoxynil (p.e.), the median value of dermal deposition to the hands being 808 microg (p.e.) compared to 1,600 microg (p.e.) for the whole body, when protective gloves were not worn. The urinary excretion pattern of bromoxynil (p.e.) did not demonstrate an obvious maximum followed by a continuous decline to background concentrations. Instead, the amounts excreted increased over the first few days after application and then tended to remain relatively constant during the remainder of the 10-day sampling period. The median value for urinary excretion was 2.22 ng x g creat(-1) x kg BW(-1) x kg (p.e.)(-1).

Comparative xenobiotic metabolism between Tg.AC and p53+/- genetically altered mice and their respective wild types

The use of transgenic animals, such as v-Ha-ras activated (TG:AC) and p53+/- mice, offers great promise for a rapid and more sensitive assay for chemical carcinogenicity. Some carcinogens are metabolically activated; therefore, it is critical that the altered genome of either of these model systems does not compromise their capability and capacity for metabolism of xenobiotics. The present work tests the generally held assumption that xenobiotic metabolism in the TG:AC and p53+/- mouse is not inherently different from that of the respective wild type, the FVB/N and C57BL/6 mouse, by comparing each genotype's ability to metabolize benzene, ethoxyquin, or methacrylonitrile. Use of these representative substrates offers the opportunity to examine arene oxide formation, aromatic ring opening, hydroxylation, epoxidation, O-deethylation, and a number of conjugation reactions. Mice were treated by gavage with (14)C-labeled parent compound, excreta were collected, and elimination routes and rates, as well as (14)C-derived metabolite profiles in urine, were compared between relevant treatment groups. Results of this study indicated that metabolism of the 3 parent compounds was not appreciably altered between either FVB/N and TG:AC mice or C57BL/6 and p53+/- mice. Further, expression of CYP1A2, CYP2E1, CYP3A, and GST-alpha in liver of naive genetically altered mice was similar to that of corresponding wild-type mice. Thus, these results suggest that the inherent ability of TG:AC and p53+/- mice to metabolize xenobiotics is not compromised by their altered genomes and would not be a factor in data interpretation of toxicity studies using either transgenic mouse line.

High cassava production and low dietary cyanide exposure in mid-west Nigeria

OBJECTIVE

To investigate if high cassava production levels indicate high consumption and high dietary cyanide exposure in three villages situated within the area of Nigeria with higher cassava production than predicted by a geographic model for cassava production in Africa.

DESIGN

Exploratory assessment of: cassava production and processing by qualitative research methods and quantification of residual cyanogens in products; cassava consumption by food frequency and weighed food records and dietary cyanide exposure by urinary thiocyanate and linamarin.

SETTING

Rural communities of Afuze, Ebue and Ofabo in mid-west Nigeria.

SUBJECTS

110 subjects from 42 households in three villages for food frequency interviews; 118 subjects in nine Ofabo households for weighed food records.

RESULTS

Cassava cultivation was reported to have increased in the preceding 20 years. It was consumed daily by 37 (88%) households, but its mean contribution to daily energy intake was only 13% The range of residual cyanogens in cassava foods was 0 to 62 mg HCN equivalent/kg dry weight (dw). Ten samples (19%) had levels above the 10 mg HCN equivalent/kg dw FAO/WHO safety limit. Mean urinary thiocyanate and linamarin were 51 and 20 micromol/L, indicating low cyanogen intake and dietary cyanide exposure.

CONCLUSION

High cassava production levels did not result in high consumption and high dietary cyanide exposure levels, therefore cassava production levels cannot be used to predict consumption or cyanide exposure levels in the study area. A large part of the production is explained by intensive sales.

Low cyanide exposure from consumption of cassava in Dar es Salaam, Tanzania

The extent of cyanide exposure from cassava consumption was studied in low income suburbs of Dar es Salaam, Tanzania. Mean cyanogen levels in sun-dried root pieces called makopa was 9.4 (range 0-79) mg HCN equivalents kg(-1) dry weight. The mean glucoside and hydrogen cyanide levels were 6.4 and 3.2 mg HCN equivalents kg(-1) dry weight, respectively, while cyanohydrins were lower with a mean of 2.0 (range 0-27) equivalents kg(-1) dry weight. Food frequency interviews with 193 schoolchildren revealed that 13% of the children consumed cassava stiff porridge in the previous week. Fried cassava pieces were consumed by 82% and boiled cassava pieces by 49% of the children. The urinary thiocyanate in these children was 36 +/- 3 (mean +/- SEM) micromol l(-1) and mean urinary linamarin level was 18 +/- 1 micromol l(-1), indicating low cyanide exposure. Multiple regression analysis revealed a positive correlation between urinary thiocyanate and consumption of boiled cassava pieces as well as between urinary linamarin levels and daily intake of fried cassava pieces.

Urinary and biliary metabolic patterns of chlorothalonil in germ-free and conventional rats

The metabolic fate of chlorothalonil, a broad spectrum fungicide that is known to be metabolized via glutathione conjugation, was examined through the analysis of urine and bile metabolites. The role of digestive microflora in the metabolism of chlorothalonil was assessed by comparing the metabolic patterns in germ-free and conventional rats. Low urinary and biliary excretion of radioactivity was observed in both conventional and germ-free rats. However, the urinary excretion of radioactivity was higher in conventional than in germ-free rats. Radio-HPLC analysis of urine and bile showed a complex metabolic profile in both conventional and germ-free rats. Methylthio metabolites of chlorothalonil were determined in ethyl acetate extracts of urine and bile of conventional and germ-free rats. These metabolites were excreted in a higher amount in the urine of conventional rats than in the urine of germ-free rats. This study shows the complexity of chlorothalonil metabolism and the role of the digestive microflora in chlorothalonil metabolism.

Ankle clonus and thiocyanate, linamarin, and inorganic sulphate excretion in school children in communities with Konzo, Mozambique

We examined 397 school children for ankle clonus in five communities in three districts affected by konzo, spastic paraparesis associated with cassava consumption. From a subsample of 131 children, we analysed urine specimens for urinary thiocyanate, linamarin, and inorganic sulphate. The proportion of children with clonus varied between sites, ranging from 4 to 22 per cent. Geometric mean thiocyanate, linamarin, and inorganic sulphate concentrations were 163 and 60 mumol/l and 4.4 mmol/l, respectively. Children with ankle clonus had higher urinary thiocyanate concentrations. We recommend prevention to reduce cyanide exposure and further monitoring of cyanide exposure and neurological damage in these communities.

Metabolic fates in humans of linamarin in cassava flour ingested as stiff porridge

Insufficiently processed products from cassava roots may contain residual amounts of cyanogenic glucosides, mainly linamarin. The fate of orally ingested linamarin was studied following a meal of cassava porridge prepared from cassava flour from southern Tanzania with 82 mg cyanide equivalents (3035 micromol) of linamarin per kg dry weight. Following ingestion of amounts of porridge containing 243-571 micromol linamarin by 15 healthy adults a mean (range) of 21% (1-47%) of the linamarin ingested was excreted in the urine within 24 hours and a mean of 1% in the next 24 hours. Serum thiocyanate, the main cyanide metabolite, increased in all subjects from a mean (+/-SD) of 34+/-26 to 78+/-28 micromol/litre (P < 0.001). In a second group of seven subjects we found that the ingestion of porridge with a mean (range) of 431 micromol (203-669%) of linamarin resulted in a mean linamarin excretion of 127 micromol/litre and an excess thiocyanate excretion of 118 micromol/litre and that 216 micromol was unaccounted for. We conclude that less than one-half of orally ingested linamarin is converted to cyanide and hence thiocyanate, about one-quarter is excreted unchanged and another quarter is metabolized into an as yet unknown compound.

Fate in humans of dietary intake of cyanogenic glycosides from roots of sweet cassava consumed in Cuba

We studied if consumption of boiled fresh roots from sweet cassava varieties grown in Cuba resulted in exposure to cyanogenic glycosides and their final breakdown product, cyanide. When adult, nonsmoking subjects consumed 1-4 kg cassava over 2 days, their urinary levels of the main cyanide metabolite, thiocyanate, only increased from a mean +/- SEM of 12 +/- 2 to 22 +/- 2 mumol/l, indicating a negligible cyanide exposure. Their mean urinary linamarin, the main cyanogenic glucoside in cassava, increased from 2 +/- 1 to 68 +/- 16 mumol/l. In a second experiment 5 subjects consumed one meal of 0.5 kg boiled cassava that contained 105 mumol linamarin and 8 mumol hydrogen cyanide (HCN). Quantitative urine collections prior to and after intake showed that 28% of linamarin was excreted during the following 24 hours, whereas a modest increase of urinary thiocyanate (SCN) only corresponded to the small amount of free HCN ingested. These results indicate that the dominant cyanogen in boiled cassava is glycosides that pass through the human body without causing cyanide exposure. It remains to be studied whether humans occasionally possess intestinal or tissue beta-glucosidases that can hydrolyse cyanogenic glycosides from cassava.

A specific and sensitive method for the determination of linamarin in Urine

A method is described for the quantitative determination of the cyanogenic glycoside linamarin. A preseparation procedure for urine samples was necessary to remove interfering substances. This was done by solid-phase extraction on a silica column containing cyclohexyl functional groups, which retained linamarin but allowed thiocyanate to pass unrestricted through the column. After elution of linamarin from the column by 35% (v/v) aqueous methanol, the glycoside was quantified following enzymatic hydrolysis, using the specified enzyme linamarase, and the free cyanide thus liberated was estimated spectrophotometrically. This method allowed quantification of linamarin in urine down to 10 mumol/l, with an estimated recovery of 91%. In 75 Tanzanian subjects consuming insufficiently processed cassava, the mean (+/- SD) urinary linamarin concentration was 104 (+/- 104) mumol/l (range 0 - 644 mumol/L), while that for thiocyanate was 486 (+/- 451) mumol/l (range 10-2,940 mumol/l), giving an approximate 1:5 molar concentration ratio between urinary linamarin and thiocyanate.

Determination of succinonitrile in horse urine by gas chromatography-nitrogen-phosphorus detector and gas chromatography-mass spectrometry

A chromatographic method was developed to detect and confirm the presence of succinonitrile (SDN) in horse urine samples, for antidoping control. The urine samples (5 ml) were extracted with diethyl ether and screened by gas chromatography-nitrogen-phosphorus detector and the confirmation of the drug's presence was accomplished by using gas chromatography-mass selective detection. The recovery of extraction was 78 and 81% for 1.0 and 2.0 micrograms ml-1 (relative standard deviation, < 10%), respectively. Urine samples collected after the administration of Energisan were positive for SDN (1-30 h) in all samples analysed.

Investigation of methacrylonitrile metabolism and the metabolic basis for the differences in its toxicity in rats and mice

Methacrylonitrile (MAN) is an industrial chemical used to manufacture plastics and elastomers. The reported p.o. LD50 of MAN is 200 to 230 mg/kg in rats and 17 mg/kg in mice. Present investigations were undertaken to further characterize MAN metabolism and to study the metabolic basis for the species differences in its toxicity. Male F344 rats and B6C3F1 mice received a single gavage dose of 11.5 or 1.15 mg of [14C]MAN/kg and were placed in glass metabolism cages. Elimination of MAN in rats occurred primarily in expired air as unchanged MAN, acetone and CO2. Three major urinary metabolites of MAN were identified as N-acetyl-S-(2-cyanopropyl)-L-cysteine, N-acetyl-S-(2-hydroxypropyl)-L-cysteine and a deoxyuridine isomer. Quantitatively, rats and mice excreted ca. 7 and 49% of the high MAN dose in urine as N-acetyl-S-(2-hydroxypropyl)-L-cysteine, respectively. In addition, rats eliminated significantly more MAN-derived CO2 and deoxyuridine than mice. MAN elimination was almost complete within 24 hr after dosing and the tissue concentrations of MAN-derived radioactivity were, with the exception of the urinary bladder, consistently higher in rats than in mice. In conclusion, a quantitative difference between rats and mice in forming the epoxide intermediate, higher efficiency of mice to conjugate this intermediate with glutathione and greater capacity of rats to degrade it to acetone and CO2 are thought to contribute to the higher sensitivity of mice to MAN acute toxicity.

Development, application and comparison of an enzyme immunoassay and a high-performance liquid chromatography method for the determination of the aromatase inhibitor CGS 20,267 in biological fluids

CGS 20,267 is a new potent and selective, nonsteroidal, oral aromatase inhibitor. For its determination in human plasma and urine, an enzyme immunoassay (EIA) and an HPLC method were developed. The EIA showed good precision and accuracy (intra- and interassay variation between 3.0 and 17.7%, recoveries between 81 and 106%) and a quantitation limit of 0.7 nmol/L. A strong cross reactivity of the antibodies with the hydroxy metabolite of CGS 20,267 (CGP 44,645) was observed. The HPLC method showed a quantitation limit in plasma of 28 and 34 nmol/L for CGS 20,267 and CGP 44,645, respectively. For urine, concentrations down to 180 nmol/L (CGS 20,267) and 210 nmol/L (CGP 44,645) could be measured. A cross check between EIA and HPLC on plasma samples from healthy male volunteers or breast cancer patients treated orally with CGS 20,267 revealed an excellent correlation (slope = 0.934, intercept = 26, r = 0.991). However, the EIA measurements of urine samples yielded 3-25 times higher concentrations than those obtained by HPLC. Further, HPLC analysis revealed the presence of CGS 20,267 and cross-reacting metabolites in urine but not in plasma. Therefore, the EIA can only be used for the determination of CGS 20,267 in plasma samples.

Analysis of the cyanogenic glycoside linamarin in urine by isotachophoresis

A separation system based on isotachophoresis is described for the cyanogenic glycoside linamarin in aqueous solution and in human urine. Isotachophoresis is a migration of a substance in an electric field, which is applied to a system of electrolytes of specific design. Detection is carried out by monitoring conductivity changes. However, for linamarin in urine, a preseparation procedure was necessary because of the high amount of electrolytes. This was performed by affinity chromatography on a silica sorbent column, with cyclohexyl as the functional group by which linamarin was retained. After elution from the column by methanol, a separation and quantitation of linamarin was possible by means of isotachophoresis. The method allowed determinations of urinary linamarin exceeding 100 microM, with a coefficient of variation of 13% at 500 microM.

Microdiffusion method with solid state detection of cyanogenic glycosides from cassava in human urine

A method for quantitative determination of cyanogenic glycosides in human urine is described. It is based on enzymatic cleavage of the glycosides, microdiffusion of the hydrogen cyanide formed, solid state detection by colour formation on a picrate-impregnated sheet, and subsequent rating of the coloured spot by the absorption of transmitted light at 540 nm with a thin-layer (TLC) densitometer. The method has been tested using normal as well as pathological urines containing glucose, protein, leucocytes, blood and bacteria. The method allows quantification of urinary linamarin above 70 mumol/litre, in 40 microliters urine. In Mozambican subjects consuming insufficiently processed cassava the mean urinary linamarin levels were 211 mumol/litre, indicating for the first time that substantial amounts of the main cyanogenic glycoside in cassava may be absorbed from the human gut and excreted intact in the urine.

Biotransformation of the antiviral agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896) and characteristics of a mesoionic ribose metabolite

The biotransformation of the antiinfluenza agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896, I) was studied. In addition to a urea metabolite (II) formed by transformation of the cyanamide functionality, another highly polar metabolite was found in mouse urine and in BSC-1, MDCK, and other cell culture incubations of [14C]LY217896. Using 13C-labeled LY217896 together with NMR and MS techniques, this highly polar metabolite was identified as a ribose derivative (III), which apparently exists in a mesoionic form (i.e. positive and negative charges within the same ring system). It was also found that this ribose is formed from LY217896 and ribose-1-phosphate in a reaction catalyzed by the enzyme purine nucleoside phosphorylase, but that the reverse reaction (cleavage of the ribose) is not observed under the conditions used. When tested in vitro using the same assay as that used to measure the antiviral activity of LY217896, this ribose and the urea metabolite exhibit essentially no activity. The presence of a ribose has been implicated in the activity of antiviral compounds such as ribavirin and anticancer agents like 2-aminothiadiazole and tiazofurin, which are structurally similar to LY217896. These activities have been postulated to involve either mono- or triphosphorylated forms, or NAD-type analogs. Possible implications of the formation of this mesoionic ribose metabolite for the mechanism of antiviral activity of LY217896 are discussed.

Alkaline diuresis for acute poisoning with chlorophenoxy herbicides and ioxynil

The relation between blood chlorophenoxy herbicide and ioxynil concentrations and toxicity, and the effect of alkaline diuresis on outcome, have been studied in 41 patients. More than one herbicide was found in 38 cases. 6 of 30 patients who had ingested chlorophenoxy compounds alone died; 16 patients (mostly in grade 3-4 coma) had alkaline diuresis and 15 survived. 7 of 11 patients who had co-ingested ioxynil died; 3 had alkaline diuresis and all survived. Alkaline diuresis reduced plasma chlorophenoxy half-lives to values observed after doses that had no adverse effects (ie, below 30 h), but did not influence ioxynil clearance. Alkaline diuresis should be used to treat acute poisoning with chlorophenoxy herbicides or ioxynil in the presence of coma or other poor prognostic indicators, such as acidaemia, or if plasma total chlorophenoxy concentrations are 0.5 g/l or more.

Metabolism of linamarin in rats

The metabolism of linamarin [2(beta-D-glucopyranosyloxy)isobutyronitrile] was investigated in male albino Wistar rats and using rat liver microsomal preparations. In the in vitro experiments incubations of varying concentrations of linamarin at pH 6.0-6.5 with liver microsomal preparations resulted in rapid degradation of the substrate without concomitant production of any detectable amount of hydrogen cyanide (HCN) or of thiocyanate, its detoxication derivative. Boiled incubation medium did not degrade linamarin. Mathematical treatment of the degradation data generated theoretical HCN values that were used to construct a Lineweaver-Burke plot, which gave apparent Km and Vmax values of 3.3 mM-linamarin and 0.017 mg HCN/min/mg protein, respectively. In the in vivo experiments excretion of glucosidic cyanide (linamarin) in rat urine was found, within the range of applied oral doses 10-350 mg/kg body weight, to be dose dependent. Urinary excretion of HCN and thiocyanate did not show this correlation. Following administration (iv) of 10, 50 or 100 mg linamarin, elimination of the test substance from rat blood was observed to occur exponentially, and the half-life was estimated at about 90 min for all three dose levels.

Influence of a cysteine prodrug, L-2-oxothiazolidine-4-carboxylic acid, on the urinary elimination of mercapturic acids of ethylene oxide, dibromoethane, and acrylonitrile: a dose-effect study

Metabolic disposition of ethylene oxide, dibromoethane, and acrylonitrile in rats after acute exposure was studied by examining the relationship between dose and urinary metabolites, and by establishing the influence of a glutathione precursor, L-2-oxothiazolidine-4-carboxylic acid (OTCA), on the above relationship. Respective urinary metabolites, hydroxyethylmercapturic acid, cyanoethylmercapturic acid, thiocyanate, and ethylene glycol, were quantified to estimate the extent to which each compound was metabolized. The animals were given either ethylene oxide (0.34, 0.68, or 1.36 mmol/kg), dibromoethane (0.2, 0.4, or 0.6 mmol/kg), or acrylonitrile (0.10, 0.38, or 0.76 mmol/kg). Urine samples were collected at 24 h. The metabolic biotransformation of all three chemicals to their respective mercapturic acids was strongly indicative of saturable metabolism. Administration of OCTA (4-5 mmol/kg) enhanced gluthathione availability and increased excretion of urinary mercapturic acids at the higher doses of the chemicals. This study indicates that OTCA increases the capacity for detoxification via the glutathione pathway thereby partially correcting the nonlinearity between the administered dose of ethylene oxide, dibromoethane, and acrylonitrile and the amount of certain urinary metabolites.

Disposition of methacrylonitrile in rats and distribution in blood components

The interaction of 2[14C]methyl-2,3[14C]acrylonitrile (MeAN) with the components of blood and its disposition in male Sprague-Dawley rats has been investigated. Following an oral administration of 100 mg/kg (0.5 LD50, 8 microCi/kg), the rats excreted 43% of the [14C] in the urine, 15% in the feces and 2.5% in the expired air as 14CO2 in 5 days. Hydrogen cyanide (H14CN) was not detectable. The red blood cells retained significant amounts of radioactivity for more than five days after administration, whereas the [14C]-activity in plasma declined sharply. More than 50% of the radioactivity in erythrocytes was detected as covalently bound to cytoplasmic (hemoglobin) and membrane proteins. A small amount of radioactivity was also found in the heme fraction. About 13% of the total dose administered was recovered as thiocyanate in the plasma and the urine. These results suggest that the toxicity of MeAN may be attributable to the whole molecule and not entirely to the in vivo liberation of cyanide.

Intermediary metabolism of 2,6-dichlorobenzonitrile (dichlobenil) in chickens and growth of chickens fed dichlobenil

1. Ten 14C-labelled metabolites were isolated from either bile (6 metabolites) or urine (7 metabolites) from chickens given single oral doses of 2,6-dichlorobenzo[14C]nitrile (14C-dichlobenil). All metabolites were benzonitriles with the following ring substituents: two Cl, OH (two isomers); Cl, two OH; Cl, OH, SH; Cl, OH, S-glutathione; Cl, OH, S-cysteinylglycine; Cl, OH, S-cysteine; and Cl, OH, S-(N-acetyl)cysteine. 2. 2-(S-Glutathionyl)-3-hydroxy-6-chlorobenzo[14C]nitrile perfused through chicken kidneys in situ was excreted in urine from the perfused kidney (44% dose) as 2-mercapto-3-hydroxy-6-chlorobenzonitrile. 3. Dichlobenil (2,6-dichlorobenzonitrile) was fed at 0, 75, 150 or 225 p.p.m. in the diet to broiler and laying strains of cockerels to determine biological activity. Feed consumption and growth were not affected, but liver and kidney weights were higher in chicks fed the dichlobenil. The percentage of lipid or nitrogen in the livers and kidneys from chicks fed dichlobenil did not differ from controls and histological or ultrastructural changes were not observed in these tissues.

Urinary excretion of acrylonitrile and its metabolites in rats

Quantitative analysis of the dose-dependent urinary excretion of acrylonitrile and its metabolites was carried out in male Wistar rats following inhalation exposure of the animals to 1, 5, 10, 50 and 100 ppm acrylonitrile for 8 h. Quantitative analysis of acrylonitrile in urine was performed by gas chromatography. The urinary metabolites cyanoethyl mercapturic acid, S-carboxymethyl cysteine and hydroxyethyl mercapturic acid were measured by a modified amino acid analysis, and thiodiglycolic acid by GC-MS. The excretion pattern of the compound and its metabolites was dependent on the exposure level; it is concluded that urinary determination of the unmetabolized acrylonitrile and two of its metabolites, cyanoethyl mercapturic acid and thioglycolic acid, may be useful for biological monitoring of industrial exposure.

Electrochemical detection of cyanogenic glycosides after enzymatic post-column cleavage

Crude and partly purified extracts from Helix pomatia and linamarase from cassava were immobilized on columns packed with porous glass or silica and used as post-column reactors in the high-performance liquid chromatography of cyanogenic glycosides. Sodium hydroxide (2 M) was added to the flowstream after the enzyme-reactor resulting in the formation of cyanide, which was then detected at a silver electrode by an amperometric measurement at 0 V with reference to a silver-silver chloride electrode. The selective detection of cyanide allows measurements in a complex matrix. The response is linear and the detection limit is in the low picomole range.

Metabolism and distribution of 3,4-epithiobutanenitrile in the rat

The metabolism and distribution of [2-14C]- and 35S-labelled 3,4-epithiobutanenitrile (4ETN), a thiirane occurring naturally in cruciferous vegetables, was studied in the rat. A dose of c. 11 mg 4ETN/kg body weight was rapidly transformed into water-soluble compounds and was mainly excreted in the urine, irrespective of the route of administration (oral or ip). The main metabolite in the urine was identified by gas chromatography-mass spectrometry as a mercapturic acid derivative. Low residual radioactivity demonstrated in organs 72 hr after administration was consistent with an earlier report that the thiirane may function as a weak biological alkylating agent.

Determination of amygdalin and its major metabolite prunasin in plasma and urine by high pressure liquid chromatography

A method is described for the determination of amygdalin and prunasin in plasma ultrafiltrate and urine. Both compounds are separated by high pressure liquid chromatography on a reversed phase column and subsequently detected at 215 nm. The identity of an amygdalin metabolite with prunasin was confirmed by mass spectrometry.

Biological monitoring of acrylonitrile exposure

A study was made of the excretion pattern of acrylonitrile (AN) in urine of 15 AN-exposed workers. During a 7-day working period with the following 2 days off, the workers delivered all their urines separately. Exposure data, collected by personal monitoring, showed a mean 8-hour TWA value of 0.13 ppm. The excretion of AN in urine (AN(U) ) showed a typical pattern; concentrations peaked at the end or shortly after the end of the workday and decreased rapidly until the beginning of the next workday. A control group of 41 nonexposed workers of the same company showed a significant increase of AN(U) with increasing number of cigarettes smoked. The AN(U) concentrations of the exposed workers however were, despite the low exposure, much higher than those of the controls, both during the workdays and during the days off. Biological monitoring of AN-exposed workers by assessing AN(U) therefore seems a very sensitive exposure evaluation method, especially because it accounts for inhalation as well as skin penetration as routes for entering the body.

Identification of two urinary metabolites of rats treated with acrylonitrile; influence of several inhibitors on the mutagenicity of those urines

Urines collected from rats injected with acrylonitrile (ACN) were mutagenic towards Salmonella typhimurium TA1530; this activity was reduced when the animals were pretreated by pyrazole (inhibitor of alcohol dehydrogenase) and suppressed after pretreatment either by CoCl2 and SKF 525-A (inhibitors of the mixed-function oxidases system) or by trichloroacetonitrile (radical trapping agent). On the other hand, two urinary metabolites (cyanoethanol and cyanoacetic acid) have been detected by gas chromatography. One possible scheme for the in vivo metabolism of ACN is presented which postulates the intermediate formation of a radical species and of an epoxide.

Identification of the major urinary metabolites of acrylonitrile in the rat

The metabolism of acrylonitrile (AN) in rats was studied in conjunction with toxicological and pharmacokinetic studies to help assess the potential hazard of exposure to AN in the workplace. Rats were administered 30 mg/kg [1-14C] AN or [2,3-14C] AN orally. Radiolabeled metabolites excreted in the urine during the first 16 h were separated by ion-exclusion liquid chromatography and identified (after derivatization) by gas chromatography-infrared spectroscopy and/or gas chromatography-mass spectrometry. Two major urinary metabolites were identified as thiocyanate and N-acetyl-S-(2-cyanoethyl)cysteine. A third was tentatively identified as 4-acetyl-3-carboxy-5-cyanotetrahydro-1,4-2H-thiazine. AN was not detected in the urine. One possible scheme for the AN metabolic pathways is proposed.

New findings on acrylonitrile metabolism

The mechanism of the metabolic pathway of acrylonitrile to cyanide (and subsequently to thiocyanate which is excreted in the urine) was already previously confirmed by our work in vitro as well as in vivo. This metabolic route of AN via glycidonitrile and glycolaldehyde cyanohydrin is not the dominant pathway in the total balance of AN metabolism and does not elucidate the fate of the predominant amount of AN. By means of AN labelled with 14C on the nitrile group it was confirmed that, when different routes of administration are used, AN forms in the rat the main portion of radioactivity excreted in the urine in "non-thiocyanate" metabolites. Based on reflection on the reactivity of AN the assumption was expressed that possible metabolites of AN may be S-(2-cyanoethyl)cysteine (CEC) or N-acetyl-S-(2-cyanoethyl)cysteine (AcCEC), so called AN-mercapturic acid. Both these substances were synthetized in our laboratory and used as standards on paper chromatography of urine of animals exposed to AN. Evidence was provided that the main metabolite of AN in rats and rabbits is AcCEC. In the urine of rats 8 hours following administration of AN-14CN in addition to AcCEC another metabolite appears the structure of which was not elucidated so far. By means of preparative paper chromatography of the methylene chloride extract of rabbit urine obtained after subcutaneous injection of AN it proved possible to isolate AcCEC in the form of its dicyclohexyammonium salt. This salt did not produce a depression of the melting point with the synthetically prepared standard. This proved unequivocally the identity of the two substances.

A simple method for the estimation of amygdalin in the urine

A procedure for the estimation of D- and D,L-amygdalin in urine is described. Amygdalin is hydrolyzed by beta-glucosidase and base to benzaldehyde, glucose and cyanide. Benzaldehyde is extracted with methylene chloride and the ultraviolet (UV) absorbence determined at 243 nm. The response of human urine "spiked" with amygdalin was linear between 10 and 75 microgram/ml. Mice administered 100 mg/kg of amygdalin intravenously or orally excreted about 70 and 20% of the administered dose, respectively, over 96 hours. In each instance more than 96% of excreted drug equivalents were obtained within the first 24 hours.