Estrogen mercapturic acids in the adult male rat

N-Acetylcysteine derivatives of catechol estrogens have been isolated from the urine of adult male hooded rats with ligated bile ducts, following injection of [4-¹⁴C]2-hydroxyestradiol-17β and of [4-¹⁴C]estradiol-17β-By application of double isotope methods previously described, it was shown that 2-hydroxyestradiol-17β was converted into mercapturic acids in a yield of 6–8%, confirming two previous experiments with bile duct cannulated rats, and that estradiol-17β was converted into mercapturic acids to the extent of 3–6%. Since these figures are small, and since it has been shown that in two women estrogen mercapturic acids were not formed, it appears that this class of compound will not provide an answer to the problem of unidentified water-soluble metabolites of the estrogens.     

Formation of mercapturic acids in rats after the administration of aralkyl esters

1. Benzylmercapturic acid and hippuric acid were isolated from the urine of rats that had been injected subcutaneously with benzyl acetate. 2. 1-Menaphthylmercapturic acid and 1-naphthoic acid were isolated from the urine of rats after the subcutaneous injection of each of the following compounds: 1-menaphthyl alcohol and its acetate, propionate, butyrate and benzoate esters. 3. A quantitative method for determining 1-menaphthylmercapturic acid in urine was developed and used to measure the excretion of this compound in the urine of rats in the 4-day period after the subcutaneous injection of 1-menaphthyl alcohol and its acetate, propionate, butyrate and benzoate esters. 4. Chromatographic evidence was obtained for the presence of S-(1-menaphthyl)glutathione and S-(1-menaphthyl)-l-cysteine in bile collected from rats with cannulated bile ducts after the animals had been injected subcutaneously with each of the following compounds: S-(1-menaphthyl)glutathione, 1-menaphthyl acetate, propionate and butyrate. 5. Benzylmercapturic acid and 1-menaphthylmercapturic acid were isolated from the urine of rats that had been injected with sodium benzyl sulphate and sodium 1-menaphthyl sulphate respectively.     

Biosynthesis of mercapturic acids from allyl alcohol, allyl esters and acrolein

1. 3-Hydroxypropylmercapturic acid, i.e. N-acetyl-S-(3-hydroxypropyl)-l-cysteine, was isolated, as its dicyclohexylammonium salt, from the urine of rats after the subcutaneous injection of each of the following compounds: allyl alcohol, allyl formate, allyl propionate, allyl nitrate, acrolein and S-(3-hydroxypropyl)-l-cysteine. 2. Allylmercapturic acid, i.e. N-acetyl-S-allyl-l-cysteine, was isolated from the urine of rats after the subcutaneous injection of each of the following compounds: triallyl phosphate, sodium allyl sulphate and allyl nitrate. The sulphoxide of allylmercapturic acid was detected in the urine excreted by these rats. 3. 3-Hydroxypropylmercapturic acid was identified by g.l.c. as a metabolite of allyl acetate, allyl stearate, allyl benzoate, diallyl phthalate, allyl nitrite, triallyl phosphate and sodium allyl sulphate. 4. S-(3-Hydroxypropyl)-l-cysteine was detected in the bile of a rat dosed with allyl acetate.     

Sensitive gas chromatographic method for determination of mercapturic acids in human urine

A method was developed for sensitive determination of the specific benzene metabolite S-phenylmercapturic acid and the corresponding toluene metabolite S-benzylmercapturic acid in human urine for non-occupational and occupational exposure. The sample preparation procedure consists of liquid extraction of urine samples followed by precolumn derivatization and a clean-up by normal-phase HPLC. Determination of analytes occurs by gas chromatography with electron-capture detection. With this highly sensitive method (detection limits 60 and 65 ng/l, respectively) urinary S-phenylmercapturic and S-benzylmercapturic acid concentrations for non-occupationally exposed persons (e.g. non-smokers) can be measured precisely in one chromatographic run. Validation of the method occured by comparison with a HPLC method we have published recently.     

Hemoglobin adducts and urinary mercapturic acids in rats as biological indicators of butadiene exposure

Binding of 1,2-epoxy-3-butene, the primary metabolite of butadiene, to hemoglobin (Hb) and excretion of its mercapturic acid in urine were studies as potential indicators of butadiene exposure. Four groups of Wistar rats were exposed to butadiene at 0, 250, 500 and 1000 ppm 6 h/day, 5 days/week, during 2 weeks. Blood was collected at the end of exposure and 17 days later for analysis of hemoglobin adducts and adduct stability. Urine was collected each day during exposure (afternoon samples) and in between exposures (morning samples). Adducts of 1,2-epoxy-3-butene to N-terminal valine in Hb were measured using the N-alkyl Edman procedure and GC/MS of the thiohydantoin derivatives. The corresponding mercapturic acid was analysed, after deacetylation, through derivatization with phthaldialdehyde and HPLC with fluorescence detection. The Hb adducts proved to be stable and are therefore useful for dosimetry of long-term exposure to butadiene. The adduct levels increased linearly with exposure dose up to 1000 ppm (3 nmol/g Hb at 1000 ppm). The increase with exposure dose of the mercapturic acid concentration in urine was also compatible with a linear does response up to 1000 ppm. The sensitivity of both analytical methods needs to be improved for their application to human samples.     

Phosphorus-containing isothiocyanate-derived mercapturic acids as a useful alternative for parental isothiocyanates in experimental oncology

A series of phosphonates, phosphinates and phosphine oxides isothiocyanate-derived mercapturic acids were synthesized. A temperature dependence dynamic proton decoupled ³¹P NMR studies indicated that in most cases the compounds were obtained as a mixture of rotamers. Moreover, biologically relevant reversibility of mercapturic acids synthesis from the parental isothiocyanates was confirmed. All compounds were evaluated as highly active antiproliferative agents in vitro in human colon cancer cell lines (LoVo and its doxorubicin-resistant subline LoVo/DX). The cell cycle progression and caspase-3 activity analyses revealed compounds moderate activity as apoptosis inducers and their poor influence on cell cycle progression in the LoVo cells. Our results confirm that isothiocyanate-derived mercapturic acids present a reasonable alternative for the parental compounds, and can replace them in the future studies on isothiocyanates potential as anticancer agents.     

Synthesis and relative stereochemistry of the four mercapturic acids derived from styrene oxide and N-acetylcysteine

The chemical reaction between (±)-styrene oxide and N-acetylcysteine produces both positional isomers ($\text{1}$ and $\text{2}$) as a mixture of diastereoisomers with a preference for the benzylic thioether isomer $\text{1}$ (2 : 1). Synthesis of the mercapturic acid conjugates from either (+)- or (?)-styrene oxide produces only two of the four possible stereoisomers. The single diastereoisomers of $\text{1}$ and $\text{2}$ were separated by high pressure liquid chromatography (HPLC) and identified by ¹H- and ¹³C-nuclear magnetic resonance (NMR). The relative stereochemistry at the benzylic carbon center of the mercapturic acid conjugates was assigned on the basis of the established chemical correlation between optically pure styrene oxide and its precursor mandelic acid, and considerations on the mechanism of ring opening of epoxides by sulfur nucleophiles. The stereochemical definition of the isomers $\text{3}$–$\text{6}$ should prove useful in investigations of the biotransformation of the glutathione (GSH) conjugates of styrene oxide.     

Determination of urinary mercapturic acids of styrene in man by high-performance liquid chromatography with fluorescence detection

A method for the determination of urinary

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(M1) and

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(M2) in man was developed. Clean-up of urine samples was obtained by a chromatographic technique using a short reversed-phase precolumn; purified samples were then deacetylated with porcine acylase I for 16 h at 37°C and deproteinized by centrifugal ultrafiltration. Derivatization was performed with o-phthaldialdehyde and 2-mercaptoethanol and the fluorescent derivatives were separated on a reversed-phase analytical column with a gradient mobile phase consisting of 50 mM acetate buffer (pH 6.5) and methanol. The retention times of the diastereoisomers of M1 (M1-“S” and M1-“R”) were 52.8 and 73.7 min, respectively; M2 diastereoisomers eluted as a single peak at 70.5 min. The fluorescence detector was set at 330 nm (excitation) and 440 nm (emission). The detection limit (at a signal-to-noise ratio of three) was about 7 μg/l. The method was applied to 25 urine samples from workers exposed to styrene. A relationship was found between urinary mandelic and phenylglyoxylic acids and mercapturic acids specific for styrene. Urine samples from ten non-exposed subjects showed no detectable amounts of analytes.     

Determination of the major mercapturic acids of acrylamide and glycidamide in human urine by LC-ESI-MS/MS

We developed a LC-MS/MS method for the quantitative determination of the mercapturic acid (MA) metabolites of acrylamide (AA) AAMA and of its oxidative metabolite glycidamide (GA) GAMA in urine samples from the general population. The method requires 4 mL of urine which is solid phase extracted prior to LC-MS/MS analysis. The metabolites are detected by ESI-tandem mass spectrometry in negative ionisation mode and quantified by isotope dilution. Detection limits ranged down to 1.5 microg/L urine for both AAMA and GAMA. The imprecision expressed as R.S.D. lay between 2% and 6% for both analytes (intra- and inter-assay). First results on a small group of 29 persons out of the general population ranged from 5 to 338 microg/L AAMA and 相似文献