N-Acetyl-S-(1-carbamoyl-2-hydroxy-ethyl)-L-cysteine (iso-GAMA) a further product of human metabolism of acrylamide: comparison with the simultaneously excreted other mercaptuic acids.

The N-acetyl-S-(1-carbamoyl-2-hydroxy-ethyl)-L: -cysteine (iso-GAMA) could be identified as a further human metabolite of acrylamide. In this study, we report the excretion of d(3)-iso-GAMA in human urine after single oral administration of deuterium labelled acrylamide (d(3)-AA). One healthy male volunteer ingested a dose of about 1 mg d(3)-AA which is equivalent to a dose of 13 microg/kg bodyweight. Over a period of 46 h the urine was collected and the d(3)-iso-GAMA levels analysed by LC-ESI-MS/MS. The excretion of iso-GAMA begins five hours after application. It rises to a maximum concentration (c (max)) of 43 microg/l which was quantified in the urine excreted after 22 h (t (max)). The excretion pattern is parallel to that of the major oxidative metabolite N-acetyl-S-(2-carbamoyl-2-hydroxy-ethyl)-L-cysteine (GAMA). Total recovery of iso-GAMA was about 1% of the applied dose. Together with N-acetyl-S-(2-carbamoylethyl)-L: -cysteine (AAMA) and GAMA, 57% of the applied dose is eliminated as mercapturic acids. The elimination kinetics of the three mercapturic acids of AA are compared. We show that dietary doses of acrylamide (AA) cause an overload of detoxification via AAMA and lead to the formation of carcinogenic glycidamide (GA) in the human body.

Hemoglobin adducts and mercapturic acid excretion of acrylamide and glycidamide in one study population.

The aim of this study was to determine the relationship between the oxidative and reductive metabolic pathways of acrylamide (AA) in the nonsmoking general population. For the first time both the blood protein adducts and the urinary metabolites of AA and glycidamide (GA) were quantified in an especially designed study group with even distribution of age and gender. The hemoglobin adducts N-carbamoylethylvaline (AAVal) and N-( R, S)-2-hydroxy-2-carbamoylethylvaline (GAVal) were detected by GC-MS/MS in all blood samples with median levels of 30 and 34 pmol/g of globin, respectively. Concentrations ranged from 15 to 71 pmol/g of globin for AAVal and from 14 to 66 pmol/g of globin for GAVal. The ratio GAVal/AAVal was 0.4-2.7 (median = 1.1). The urinary metabolites were determined by LC-MS/MS. Of all urine samples examined 99% of N-acetyl- S-(2-carbamoylethyl)- l-cysteine (AAMA) levels and 73% of N-( R/ S)-acetyl- S-(2-carbamoyl-2-hydroxyethyl)- l-cysteine (GAMA) levels were above the LOD (1.5 microg/L). Concentrations ranged from

Investigations on permeation of mitomycin C through double layers of natural rubber gloves.

Treating peritoneal carcinomatosis by the aggressive cytoreductive surgery with the hyperthermic intraoperative intraperitoneal chemotherapy (HIPEC) surgeons expose their gloved hands for up to 90 min to a peritoneal dialysis solution (PDS) containing mitomycin C (MMC). We investigated the permeation of MMC through the material of three different natural rubber gloves under conditions similar to the in-use during HIPEC as well as under worst-case exposure scenario. Two different methods, a two-chamber diffusion cell and a single-chamber glass chamber method, were used to demonstrate the permeation capability. The permeation of MMC dissolved in 0.9% NaCl solution and PDS through double natural rubber glove material was tested over 2 h using four concentrations (c = 0.004, 0.008, 0.016 and 0.4 mg ml(-1)) and three receptor fluids (0.9% NaCl solution, PDS and a novel artificial sweat). In none of four glass chamber experiments and in only one of 40 diffusion cell experiments was permeation through glove material detected. The permeation occurred between 15 and 30 min under worst-case exposure scenario at a approximately 100-fold higher MMC concentration than under in-use conditions during HIPEC. The double-layer natural rubber gloves tested were effective to prevent a permeation of MMC in vitro under HIPEC-similar exposure. Our results support the glove wearing procedure in our university hospital. However, occupational exposure to antineoplastic drugs should be minimized, since there is insufficient knowledge regarding harmful effects from a long-term exposure to low doses.

Urinary excretion of acrylamide and metabolites in Fischer 344 rats and B6C3F(1) mice administered a single dose of acrylamide.

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in mice and rats. AA is also formed during cooking in many commonly consumed starchy foods. Our previous toxicokinetic investigations of AA and its genotoxic metabolite, glycidamide (GA), in rodents showed that AA is highly bioavailable from oral routes of administration, is widely distributed to tissues, and that the dietary route, in particular, favors metabolism to GA. Formation and accumulation of mutagenic GA-DNA adducts in many tissues support the hypothesis that AA is carcinogenic in rodent bioassays through metabolism to GA. The current investigation describes the quantification of 24 h urinary metabolites, including free AA and GA and their mercapturic acid conjugates (AAMA and GAMA, respectively), using LC/MS/MS in F344 rats and B6C3F(1) mice following a dose of 0.1 mg/kg bw given by intravenous, gavage, and dietary routes of administration. Similar groups of rodents were used previously for serum/tissue toxicokinetic and adduct determinations (DNA and hemoglobin). The goal was to investigate relationships between urinary and circulating biomarkers of exposure, toxicokinetic parameters for AA and GA, and tissue GA-DNA adducts in rodents from single doses of AA. Significant linear correlations were observed between urinary levels of AA with AAMA and GA with GAMA in the current data sets for rats and mice. Concentrations of AA and AAMA correlated significantly with average AUC values determined previously for AA in groups of rats and mice similarly dosed with AA. Urinary GA and GAMA concentrations showed significant correlations with average AUC values for GA and liver GA-DNA adducts determined previously in rats and mice similarly dosed with AA. Despite statistical significance, considerable inter-animal variability was observed in all urinary measurements, which limited the degree of correlation with either average toxicokinetic or biomarker data collected from different groups of animals. These results suggest that urinary measurements of AA and its metabolites may be useful for prediction of internal exposures to AA and GA.

Acrylamide exposure via the diet: influence of fasting on urinary mercapturic acid metabolite excretion in humans.

Acrylamide (AA) is carcinogenic in animals and classified by the International Agency for Research on Cancer as probably carcinogenic in humans. Regarding the AA contents of food the diet significantly contributes to the overall AA burden of the general population. However, it is unclear to which degree the diet, apart from smoking, contributes to the internal AA exposure. Therefore the influence of an AA-free diet on the excretion of urinary mercapturic acid metabolites derived from AA in three healthy volunteers fasting for 48 h was examined. Urinary AA mercapturic acid metabolites were considerably reduced after 48 h of fasting. The levels were even well below the median level in non-smokers. This confirms that the diet is the main source of environmental AA exposure in humans, apart from smoking. Other possible AA sources could be of minor quantitative importance only.

Toxicokinetics of acrylamide in humans after ingestion of a defined dose in a test meal to improve risk assessment for acrylamide carcinogenicity.

High amounts of acrylamide in some foods result in an estimated daily mean intake of 50 microg for a western style diet. Animal studies have shown the carcinogenicity of acrylamide upon oral exposure. However, only sparse human toxicokinetic data is available for acrylamide, which is needed for the extrapolation of human cancer risk from animal data. We evaluated the toxicokinetics of acrylamide in six young healthy volunteers after the consumption of a meal containing 0.94 mg of acrylamide. Urine was collected up to 72 hours thereafter. Unchanged acrylamide, its mercapturic acid metabolite N-acetyl-S-(2-carbamoylethyl)cysteine (AAMA), its epoxy derivative glycidamide, and the respective metabolite of glycidamide, N-acetyl-S-(2-hydroxy-2-carbamoylethyl)cysteine (GAMA), were quantified in the urine by liquid chromatography-mass spectrometry. Toxicokinetic variables were obtained by noncompartmental methods. Overall, 60.3 +/- 11.2% of the dose was recovered in the urine. Although no glycidamide was found, unchanged acrylamide, AAMA, and GAMA accounted for urinary excretion of (mean +/- SD) 4.4 +/- 1.5%, 50.0 +/- 9.4%, and 5.9 +/- 1.2% of the dose, respectively. Apparent terminal elimination half-lives for the substances were 2.4 +/- 0.4, 17.4 +/- 3.9, and 25.1 +/- 6.4 hours. The ratio of GAMA/AAMA amounts excreted was 0.12 +/- 0.02. In conclusion, most of the acrylamide ingested with food is absorbed in humans. Conjugation with glutathione exceeds the formation of the reactive metabolite glycidamide. The data suggests an at least 2-fold and 4-fold lower relative internal exposure for glycidamide from dietary acrylamide in humans compared with rats or mice, respectively. This should be considered for quantitative cancer risk assessment.

Excretion of mercapturic acids of acrylamide and glycidamide in human urine after single oral administration of deuterium-labelled acrylamide.

We investigated the human metabolism of AA to the mercapturic acids N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R/S)-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L: -cysteine (GAMA) which are derived from AA itself and from its oxidative genotoxic metabolite glycidamide (GA), respectively. A healthy male volunteer received a single dose of about 1 mg deuterium-labelled acrylamide (d(3)-AA), representing 13 microg/kg body weight, in drinking water. Urine samples before dosing and within 46 h after the dose were analysed for d(3)-AAMA and d(3)-GAMA by LC-ESI-MS/MS. A first phase of increase in urinary concentration was found to last 18 h with a broad plateau between 8 and 18 h for AAMA, and 22 h for GAMA. Elimination half-lives of both AAMA and GAMA were estimated to be approximately 3.5 h for the first phase and more than 10 h up to few days for the second phase. Total recovery in urine after 24 h was about 51% as the sum of AAMA and GAMA and hereby well in accordance with former studies in rats. After 2 days AAMA, accounting for altogether 52% of the total AA dose, was the major metabolite of AA in humans. GAMA, accounting for 5%, appeared as a minor metabolite of AA. In humans we found a urinary ratio of 0.1 for GAMA/AAMA compared to previously reported values of 0.2 for rats and 0.5 for mice. Therefore, the metabolic fate of AA in humans was more similar to that in rats than in mice as already demonstrated in terms of the haemoglobin adducts. Consequently a genotoxic potency of AA mediated by GA could be supposed to be comparable in rats and humans.