Search

Acrylonitrile (AN) is a rat carcinogen. Human exposure may come from chemical industries and smoking. A haemoglobin adduct of acrylonitrile (Hb-AN) has been used as a biomarker of exposure by means of gas chromatography-mass spectrometry (GC-MS) analysis. We have developed specific monoclonal antibodies (Mab) to human Hb-AN and wish to report evaluation of an immunoassay in rats using an Mab that cross-reacts with rat Hb-AN. A dose response study of LD 0, 10, 50, and 90 in Sprague-Dawley rats was undertaken, with each rat receiving [2,3- 14 C]AN at 50 μCi kg -1 sc, and Hb from an aliquot of blood was taken for covalent binding analysis by liquid scintillation spectrometry and fluorescence ELISA. The dose responses of rats at 0.25, 0.5, 1.0, and 2.0 h after AN doses of 20, 50, 80, 115 mg kg -1 were compared by both methods with Hb and globin samples. Regression analysis showed a linear relationship between immunoassay and 14 C-AN binding. This indicates that an antigenic form of Hb-AN may be used as a surrogate of Hb-AN adduct. The sensitivity of ELISA was tested in rats exposed for 1 h to sub-toxic doses of AN (10-1.1 mg kg -1 ). Quantification of Hb-AN by immunoassay was achieved by calibration with a synthetic adduct HbAN4h, a reference adduct prepared by treating rat Hb with excess AN for 4 h. ELISA and GC-MS analysis of N-terminal valine-AN in the Hb-AN adduct were compared and similar detection levels were found. This rat study appears to have validated the new immunoassay method for biomonitoring of AN exposure.

Three markers of acute acrylonitrile (AN) intoxication, namely, tissue glutathione (GSH), tissue cyanide (CN), and covalent binding to tissue protein, were studied as a function of dose and time. Doses administered and responses expected were 20 mg/kg (LD0), 50 mg/kg (LD10), 80 mg/kg (LD50), and 115 mg/kg (LD90). Liver GSH was the most sensitive marker of AN exposure. At 80 mg/kg AN, virtually complete depletion of liver GSH was observed within 30 min with no recovery through 120 min. Kidney GSH showed a similar, but less intense depletion; while blood and brain GSH were more refractory to AN. Whole blood and brain CN rose progressively during the first 60 min in a dose-dependent fashion. At the lowest dose, CN levels decreased thereafter, whereas, at the three higher doses, CN levels were maintained or continued to increase through 120 min. At the highest dose, blood and brain CN remained at acutely toxic levels through 240 min. Covalent binding increased rapidly in all tissues during the first 30 min at all doses. At the lowest dose, little additional covalent binding was observed beyond 30 min, while at the three higher doses, covalent binding increased, although at a slower rate. The data indicate that these three biologic markers of acute AN intoxication respond dramatically in a time-dependent manner in the toxic dosage range. Furthermore, the data provide evidence that AN toxicity is gated by GSH depletion in liver with the resultant termination of AN detoxification.

Ethanol and a variety of other compounds previously have been shown to acutely inhibit the metabolism of ethyl carbamate (EC) when given concurrently in mice. On the other hand, ethanol pretreatment (10% in drinking water for the period 48 to 12 hr prior to EC treatment) is known to have the opposite effect and enhance the clearance of EC from blood of mice. In the present work, acetone has been shown to act similarly. Concurrent acetone treatment inhibits the metabolism of EC (11.1 mg/kg po) in male A/JAX mice in a dose-response manner. Blood clearance (Cl) of this po dose of EC from mice following concurrent acetone treatment (50 mg/kg, 0.86 mmol/kg ip) averaged 185 +/- 5.4 (SE) ml hr-1 kg-1 vs. controls of 804 +/- 24.6 ml hr-1 kg-1. Comparing doses that produce equal effects on the blood clearance values of EC, acetone is approximately 50-fold more potent as an inhibitor than ethanol. Pretreatment of mice with acetone (2 g/kg ip) 48 hr and 24 hr before EC administration po increased the clearance of EC approximately 3-fold (CI = 2623 +/- 123 ml hr-1 kg-1). 2-Propanol was found to be at least as potent as inhibitor as acetone, but with a longer duration of inhibition; this longer duration was explained by the longer persistence of acetone in blood from conversion of 2-propanol to acetone.(ABSTRACT TRUNCATED AT 250 WORDS)

Incubation of ribonuclease with 0.1M mercaptoethanol at pH 8.5 can increase the enzyme's hydrolytic activity toward cytidine 2',3'-monophosphate (cyclic CMP) under standard assay conditions. Cation-exchange chromatography of the ribonuclease-thiol reaction mixture revealed seven fractions. The fraction with the highest activity had an approximate tenfold decrease in the apparent Michaelis constant for cyclic CMP with respect to native ribonuclease. The enhanced activity is a metastable property since this fraction reverts back to the control activity and chromatographic behavior of native ribonuclease on standing in solution at room temperature.

The importance of the 3-methyl group on the pyridinium ring of bis-quaternary nitrogen salts for hemicholinium-3-like activity having been conditionally established (Benz & Long, 1969a, b), derivatives containing classical isosteres of the 3-methyl group and the three oxidation states of the 3-methyl group were examined. Oxidation of the 3-methyl group to -CH2OH decreased activity tenfold. Subsequent oxidation to -CHO and -COOH further decreased activity. When the 3-methyl group was replaced by a halogen, activity was maintained by the iodo-derivative but decreased as the size of the halogen decreased and as the electronegativity increased. Substitution of an ethyl group for the 3-methyl decreased activity twofold, whereas replacement with -OH eliminated activity.