32P-post-labelling of 7-(3-chloro-2-hydroxypropyl)guanine in white blood cells of workers occupationally exposed to epichlorobydrin

Abstract

Epichlorohydrin (ECH) is a simple 3-carbon epoxide of industrial importance. It has been shown to be genotoxic in several systems and carcinogenic in experimental animals. The aim of the present investigation was to study DNA adducts of ECH as a biomarker of occupational exposure to this chemical. 7-(3-Chloro-2-hydroxypropyl)guanine (7-CHP-guanine) was analysed in DNA from white blood cells using an anion exchange-based adduct enrichment protocol of the 32P-post-labelling/HPLC-based assay. Blood samples were collected from seven workers handling ECH (exposed), nine workers not handling ECH but normally present in the premises where this chemical is used (potentially exposed) and 13 office and factory workers from locations in the plant where ECH is not handled (controls). 7-CHP-guanine was detected in five of the seven workers exposed to ECH (1.6-7.1 mol/109 mol nucleotides) and in two of the nine workers potentially exposed to ECH (0.8-1.5 mo/109 mol nucleotides). This adduct was not detected in any of the 13 controls. The difference in adduct levels between exposed workers and controls was statistically significant (Mann-Whitney test, P < 0.001), as was the difference between exposed workers and potentially exposed workers (P = 0,017). The recovery of 7-CHP-guanine in the 32P-post-labelling assay was on average 48 ± 7%, which is considerably higher than previously reported for other 7-alkylguanines. The method used had a limit of detection of ~0.4 mol adduct/109 mol nucleotides using 20 μg DNA. This study shows for the first time ECH-induced DNA adducts in humans and suggests that 7-CHP-guanine may be used as a biomarker of occupational exposure to ECH.