Monitoring exposure to acrylonitrile using adducts with N-terminal valine in hemoglobin

Abstract

Human exposure to acrylonitrile (ACN), a carcinogen in rats, may occur in industrial settings, through waste water and tobacco smoke. ACN is an electrophilic compound and binds covalently to nucleophilic sites in macromolecules. Measurements of adducts with hemoglobin could be utilized for improved exposure assessments. In this study, a method for quantification of N-(2-cyanoethyl)valine (CEVal), the product of reaction of ACN with N-terminal valine in hemoglobin has been developed. The method is based on the N-alkyl Edman procedure, which involves derivatization of the globin with pentafluorophenyl isothiocyanate and gas chromatographic-mass spectrometric analysis of the resulting thiohydantoin. An internal standard was prepared by reacting valylglycylglycine with [2H3]ACN, spiked with [14C]ACN to a known sp. act. Levels of CEVal were measured in globin from rats exposed to 3-300 p.p.m. ACN in drinking water for 105 days and from humans (four smokers and four non-smokers). CEVal was detected at all exposure levels in the drinking water study. The relationship between adduct level and water concentration was linear at concentrations of 10 p.p.m. (corresponding to an average daily uptake of c. 0.74 mg ACN/kg body wt during the 65 days prior to sacrifice) and below, with a slope of 37.7 pmol CEVal/g globin/p.p.m. At higher concentrations, adduct levels increased sublinearly, indicating saturation of a metabolic process for elimination of ACN. Comparison of adduct formation with the estimated dose (mg/kg/day) of ACN indicated that at low dose (0-10 p.p.m.) CEVal = 0.508 x ACN dose + 0.048 and at high dose (35-300 p.p.m.) CEVal = 1.142 x ACN dose - 1.098. Globin from the smokers (10-20 cigarettes/day) contained about 90 pmol CEVal/g, whereas the adduct levels in globin from non-smokers were below the detection limit. The analytical sensitivity should be sufficient to allow monitoring of occupationally exposed workers at levels well below the current Occupational Safety and Health Administration standard of 2 p.p.m.

Biomonitoring of 1,3-butadiene and related compounds.

“…Several low molecular weight adducts with N-terminal valine in hemoglobin, including the adducts of epoxybutene, ethylene oxide (74), styrene oxide (75), and acrylonitrile (76), have been studied in experimental animals and appear to be chemically stable at low exposure levels. Tates (77) studied hydroxyethylvaline in hemoglobin of four workers accidentally exposed to high concentrations of ethylene oxide.…”

Synthesis and characterization of peptide adducts for use in monitoring human exposure to acrylonitrile and ethylene oxide

“…This may be extracted, derivatized if appropriate, and determined by GC-MS using selected ion monitoring and normally a stable isotope-labeled internal standard. This approach has been applied in particular to adducts formed by low molecular weight epoxides (e.g., ethylene oxide [3], propylene oxide [4], 1,3-butadiene epoxide [ 5 ] , styrene oxide [6]), and by acrylamide [7], acrylonitrile [8], and methylating agents [9]. Occupational and environmental exposure (notably from cigarette smoke) to these compounds have been monitored.…”

“…A more appropriate internal standard, to overcome the difficulties of the above two possibilities, would be an adducted peptide [8]. This could be made pure (i.e., of known adduct content/weight) and should also behave in a similar way during the Edman degradation procedure to the adducted protein.…”

Verwendung von H�moglobinaddukten als Biomarker f�r das Monitoring von Belastungen und Beanspruchungen durch gentoxische Stoffe

“…Umso wichtiger ist es aber, das Vorkommen dieser Stoffe in Umweltmedien, Nahrungsmitteln und Verbraucherprodukten zu untersuchen, Hintergrundbelastungen zu charakterisieren,die Auswirkungen besonderer Expositionen auf die innere Belastung und Beanspruchung betroffener Personen zu quantifizieren und die inkrementelle Erhöhung der inneren Belastung und Beanspruchung durch spezifische Expositionen zu bewerten. Beispiele aus der Literatur sind in Tabelle Zu den untersuchten Alkylantien gehören: Epoxide (Ethylenoxid, Propylenoxid, [6]), ungesättigte aliphatische Verbindungen (Acrylnitril, [7]) und solche, die im Stoffwechsel zu Epoxiden metabolisiert werden (Ethylen, Propylen, Butadien, Styrol [8]). Des Weiteren sind methylierende Substanzen wie Methylhalogenide und Dimethylsulfat zu erwähnen [9].…”