Marc Potvin

Acidic metabolites of pseudocumene in rabbit urine.

In order to identify biological indicators of exposure to trimethylbenzenes, the metabolism of pseudocumene (1,2,4-trimethylbenzene) was investigated in rabbits. After oral administration of this compound, urine was collected for several days and analyzed for the presence of acidic metabolites. Isolation techniques included steam-distillation, direct extraction of urine by ethyl acetate, preparative thin-layer and column chromatography of the extract. The metabolites were identified by microanalysis, followed by TLC, gas chromatography-mass spectrometry, infrared and ultraviolet spectroscopy. Two major urinary metabolites were identified, namely 2,4-dimethylbenzoic acid and 3,4-dimethylhippuric acid. The presence of these acidic metabolites in urine is a good indication of exposure to pseudocumene.

Studies on inhalation toxicity of 2-propanol.

Biological effects of a single exposure to moderate or high concentrations of 2-propanol were investigated in Sprague-Dawley rats. Acute toxicity (LC50, t:8 hours) of this widely used solvent was determined and found to be 19000 ppm (17380-20760 ppm) for females and 22500 ppm (19200-26400 ppm) for males. Determination of blood levels of 2-propanol and its metabolite, acetone, was carried out during and after a single 4-hour exposure (Concentration range: 500 to 8000 ppm). The amount of acetone and 2-propanol was directly related to the various air concentrations of alcohol inhaled. Increase of exposure time to 8 hours enhanced considerably the amount of blood acetone which could be determined even 20 hours after exposure. These findings indicate a slow conversion of this alcohol to acetone which can be used as biochemical indicator to exposure. Histopathological examination of rats exposed to high levels of 2-propanol shows typical lesions of chemical pneumonitis and pulmonary edema accompanied by foamy vacuolization of liver cells and severe focal cytoplasmic degradation.

Biological Conversion of Benzaldehyde to Benzylmercapturic Acid in the Sprague-Dawley Rat

The metabolism of benzaldehyde was investigated in Sprague-Dawley rats. After repeated oral administration of this compound (0.4-1.0 g/kg) for 13 consecutive days, urine was collected and analyzed for the presence of metabolites. The acidification of the pooled urine samples (pH:2.0) with 6 N H2SO4 was followed by ethyl acetate extraction, evaporation of the extract and methylation with diazomethane. Identification of the metabolite by comparison with a synthetic sample of benzylmercapturic acid (BENZM) was conducted by gas chromatography. Mass spectrometry examination of this metabolite revealed the following peaks characteristic of benzylmercapturic acid: m/z (%), 91(100), 176(27), 208(23), 43(20), 88(13), 117(10), 134(9), M+ 267(2). Monitoring of urines from both female and male rats showed a dose-related increase of benzylmercapturic acid which was found to be a reliable indicator of exposure to benzaldehyde.

SUBACUTE INHALATION TOXICITY OF BENZALDEHYDE IN THE SPRAGUE-DAWLEY RAT

Benzaldehyde was administered by inhalation to female and male Sprague-Dawley rats for 14 consecutive days (low level: 500 ppm; medium level: 750 ppm; high level: 1000 ppm). Effects of this chemical were investigated during and at the end of the exposure period. Throughout the experiment, significant hypothermia and a reduction of motor activity were observed in all rats exposed to benzaldehyde and were accompanied in high-level rats by a severe impairment of the central nervous system, as evidenced by abnormal gait, tremors, and a positive Straub sign. Histopathologic examination of tissues from exposed rats showed a goblet cell metaplasia that was largely confined to the respiratory epithelium lining the nasal septum in male rats. No other abnormal microscopic changes were observed. A no effect level was not observed in these studies.

Metabolism of benzaldehyde in New Zealand White rabbits

The quantitative metabolism of benzaldehyde (BENZ) has been investigated in male New Zealand White rabbits (3 rabbits/group). A single oral dose of this material was administered to two test groups (low-dose group: 0.35 g/kg/rabbit; high-dose group: 0.75 g/kg/rabbit) whereas water (0.75 g/Kg/rabbit) was given orally to the third group. Urine of all groups was collected daily for 15 consecutive days. Daily monitoring indicated the urinary excretion of the following metabolites: hippuric acid (HA), free (FBA) and conjugated benzoic acid (benzoylglucuronic acid: BGA), benzyl glucuronide (BG) and benzyl mercapturic acid (BMA). Although the total amount of urinary metabolites excreted by the low-dose group (83.2% of the total dose) was not significantly different from that excreted by the high-dose group (82.3% of the total dose), some metabolites showed differences in their urinary output: HA, 69.9% in the low-dose group vs. 66.7% in the high-dose group; BGA, 8.8% in the low-dose group vs. 11.2% in the high-dose group; BG, 2.9% in the low-dose group vs. 3.0% in the high-dose group; FBA, 1.6% in the low-dose group vs. 1.4% in the high-dose group. In both treated groups, BMA was present in trace amounts (< 0.01% of the total dose).

Biological Conversion of N-Phenyl-2-Naphthylamine to 2-Naphthylamine in the Sprague-Dawley Rat

The metabolism of a widely used plastic and rubber antioxidant, N-Phenyl-2-Naphthylamine, was investigated in Sprague-Dawley rats. After repeated oral administration of this compound, urine and feces were collected for several days and analyzed for the presence of metabolites. Identification techniques included a preliminary clean-up followed by thin-layer chromatography of amines and gas chromatography-mass spectrometry of their hexafluoroacyl derivatives (HFBA). The compounds identified in both urine and feces were characterized as N-Phenyl-2-Naphthylamine (PBNA) and 2-Naphthylamine (BNA). Data obtained on urinary excretion of BNA seem to indicate that repeated administration of PBNA enhances its own metabolism.

Identification and determination of mesitylene acidic metabolites in rabbit urine

Analytical methodology was developed to identify acidic metabolites of mesitylene and to assess their excretion in the urine of New Zealand White rabbits. After oral administration of a single dose...

Metabolism of furfural in the Sprague‐Dawley rat

The metabolism of furfural was investigated in Sprague‐Dawley (SD) rats. Analytical methodology was developed to identify urinary metabolites by gas chromatography‐mass spectrometry (GC‐MS). Ten adult male SD rats (average weight: 490±20 g) were administered a single oral dose of furfural (50 mg/ kg/rat) and urines were collected for 3 consecutive days. Freshly voided urine was obtained from the rats and analyzed for the presence of metabolites. A 2mL urine sample was adjusted to pH 1.4 using 6N H2SO4, followed by ethyl acetate extraction (2x4mL). The extract was evaporated and dissolved in a mixture of ethyl ether/methanol (9/1) for methylation with diazomethane. The mixture was evaporated to near dryness and dissolved in 2mL methanol. Identification of the metabolites as methyl esters by comparison with synthetic samples was conducted by gas chromatography on a DB‐5 capillary column. Further identification of the metabolites was conducted by mass spectrometry which revealed peaks characteristic of 2‐fur...

Comparative N-dephenylation of N-phenyl-2-naphthylamine in Sprague-Dawley rats and New Zealand White rabbits

Abstract The comparative conversion of N-phenyl-2-naphthylamine (PBNA) to 2-Naphthylamine (BNA) has been investigated in Sprague-Dawley rats and New Zealand White rabbits. After repeated administration of this compound by gavage to both species (200 mg/kg/day/4 days), urine and feces were collected daily for four days and analyzed for metabolites. A preliminary cleanup (pH: 9.0) was followed by thin-layer chromatography and gas chromatography/mass spectrometry of heptafluoroacyl (HFBA) derivatives of PBNA and BNA which were identified in urines and feces of both species. Monitoring of urine and feces during the four-day dosing indicated an enhanced excretion of PBNA and its metabolite, BNA in these species. Cumulative urinary excretion of both compounds in rabbits was found to be much higher than that observed in rats: for the same dose level used, rabbits excreted 20 times more PBNA and 14 times more BNA than rats.