1-Bromopropane (1-BP, CAS 106-95-5), an alternative solvent to chlorofluorocarbons, has been reported to cause reproductive and neurotoxicity in male rats. The related 2-bromopropane has been shown to cause similar toxicity in rats and amenorrhea, oligozoospermia, and anemia in workers. Activation to reactive intermediates may be important. Metabolism of 1-BP is complex, including debromination, CYP2E1 oxidation and glutathione S-conjugation. The formation of 3-bromopropionic acid and n-propanol as well as of S-n-propyl-glutathione, S-n-propyl-L-cysteine and the mercapturic acids N-acetyl-S-(n-propyl)-L-cysteine (M1), N-acetyl-S-(n-propyl)-L-cysteine-S-oxide (M2), N-acetyl-S-(2-carboxyethyl)-L-cysteine (M3), and N-acetyl-S-(3-hydroxy-n-propyl)-L-cysteine (M4). A potential biomonitoring method was developed to measure urinary levels of M1, M2, M3 and M4. Standards and a stable isotope-labeled analog of M1 as internal standard were synthesized using the general procedure of van Bladern et al. (1980). Samples mixed with internal standard were loaded onto Bond Elute C18 SPE columns. A fraction containing >90% of 1-BP metabolites was eluted with acetone for analysis by HPLC ESI-MS/MS on a 150X2 mm Phenomenex Aqua C18 column using a 10-min H2O:MeOH (1% acetic acid) linear gradient at 300 L/min. The ESI-MS/MS operated in the positive ion mode to detect protonated M1, M2, M3 and M4 and used Selected Reaction Monitoring of major transition products. Urine samples fortified with standards were mixed with 10 g/mL internal standard and evaluated for recovery, limits of detection and limits of quantitation. Calibration of M1, M2, M3 and M4 was linear from 30 - 10000 ng/mL (r2>0.99). Sample preparation and analysis appears to offer significant advantages over typical derivatization that would be required for GC-MS analysis of these compounds. Thus, 1-BP internal exposure levels for various exposure situations can be rapidly determined by analysis of these metabolites in a single assay using selective sample preparation.
The Toxicologist. Society of Toxicology 41st Annual Meeting and ToxExpo, March 17-21, 2002, Nashville, Tennessee