Comparison of the mutations at Hprt exon 3 of T-lymphocytes from B6C3F1 mice and F344 rats exposed by inhalation to 1,3-butadiene or the racemic mixture of 1,2 : 3,4-diepoxybutane
Qx. Meng et al., Comparison of the mutations at Hprt exon 3 of T-lymphocytes from B6C3F1 mice and F344 rats exposed by inhalation to 1,3-butadiene or the racemic mixture of 1,2 : 3,4-diepoxybutane, MUT RES-GTE, 464(2), 2000, pp. 169-184
Citations number
35
Categorie Soggetti
Molecular Biology & Genetics
Journal title
MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS
Experiments were conducted to define the spectra of mutations occurring in
Hprt exon 3 of T-cells isolated from spleens of female B6C3F1 mice and F344
rats exposed by inhalation to 1,3-butadiene (BD) or its reactive metabolit
e, (+/-)-diepoxybutane (DEB). Hprt mutant frequencies (Mfs) in BD-exposed (
1250 ppm for 2 weeks or 625 ppm for 4 weeks; 6 h/day, 5 days/week) and DEB-
exposed (2 or 4 ppm for 4 weeks or 5 ppm for 6 weeks; 6 h/day, 5 days/week)
mice and rats were significantly increased over concurrent control values.
Mutant T-cell colonies from control and treated animals were screened for
mutations in Hprt exon 3 using PCR amplification of genomic DNA and denatur
ing gradient gel electrophoresis, followed by sequence analysis. Exon 3 mut
ations were found at the following frequencies: 20/394 (5%) in control mice
, 56/712 (8%) in BD-exposed mice, 59/1178 (5%) in BD-exposed rats, 66/642 (
10%) in DEB-exposed mice, and 51/732 (7%) in DEB-exposed rats. Mutations in
exposed animals included base substitutions, small deletions (1 to 74 bp),
and small insertions (1 to 8 bp), with base substitutions predominating. A
mong the types of base substitutions observed in mice, the proportions of G
. C --> A . T transitions (p = 0.035, Fisher's Exact Test) and G . C --> C
. G transversions (p = 0.05) were significantly different in control vs. B
D-exposed animals. Given the small number of exon 3 mutants analyzed, there
was a high degree of overlap in the mutational spectra between BD-exposed
mice and rats, between BD- and DEB-exposed mice, and between BD- and DEB-ex
posed rats in terms of the sites with base substitutions, the mutations fou
nd at those mutated sites, the relative occurrence of the most frequently o
bserved base substitutions, and the occurrence of a consistent strand bias
for the most frequently observed base substitutions. The spectra data sugge
st that adduction of both G . C and A . T bps is important in the induction
of in vivo mutations by BD metabolites in exposed mice and rats. (C) 2000
Elsevier Science B.V. All rights reserved.