Molecular dosimetry of ethylene oxide: formation and persistence of 7-(2-hydroxyethyl)guanine in DNA following repeated exposures of rats and mice.
The formation of 7-(2-hydroxyethyl)guanine (7-HEG) in DNA of target and nontarget tissues was investigated in male B6C3F1 mice (20/group) and F344 rats (10/group) exposed to 0, 3, 10, 33, 100, or 300 (rats only) ppm ethylene oxide (ETO) by inhalation for 6 h/day for 4 weeks (5 days/week) and mice exposed to 100 ppm ETO for 1 or 3 days or 1, 2, or 4 weeks (5 days/week). The persistence of 7-HEG was studied in mice killed up to 7 days after cessation of the 4-week time-course study. In addition, the formation of O6-(2-hydroxyethyl)guanine and 3-(2-hydroxyethyl)adenine was evaluated in rats exposed to 300 ppm ETO. DNA samples from control and treated animals were analyzed for 7-HEG using neutral thermal hydrolysis, microconcentration, and high-performance liquid chromatography separation with fluorescence detection. Fluorescence-linked high-performance liquid chromatography was used for O6-(2-hydroxyethyl)guanine quantitation, and immunochromatography and gas chromatography-mass spectrometry were used for 3-(2-hydroxyethyl)adenine detection. Analysis of DNA from tissues of control mice and rats revealed the presence of peaks equivalent to 2-6 pmol 7-HEG/mg DNA. In mice exposed to 100 ppm ETO, 7-HEG accumulated to a similar extent in target and nontarget tissues, with adduct concentrations ranging from 17.5 +/- 3.0 (SE) (testis) to 32.9 +/- 1.9 (lung) pmol adduct/mg DNA after 4 weeks of exposure. Concurrent exposures of mice and rats to 100 ppm ETO for 4 weeks led to 2- to 3-fold lower concentrations of 7-HEG in mouse DNA in all tissues compared to rat DNA. 7-HEG disappeared slowly in a nearly linear fashion from the DNA of mouse kidney (t1/2 = 6.9 days) and rat brain and lung (t1/2 = 5.4-5.8 days), which was consistent with the loss of adduct mainly by chemical depurination. In contrast, a more rapid removal of 7-HEG from other mouse (t1/2 = 1.0-2.3 days) and rat (t1/2 = 2.9-4.8 days) tissues was consistent with adduct loss by depurination and DNA repair. Dose-response relationships for 7-HEG were nonlinear in both mice and rats, with the alkylating efficiency of ETO increasing at high exposures.(ABSTRACT TRUNCATED AT 400 WORDS)
Walker
V E
VE
Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina 27709.
Fennell
T R
TR
Upton
P B
PB
Skopek
T R
TR
Prevost
V
V
Shuker
D E
DE
Swenberg
J A
JA
D000280:Administration, Inhalation; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005027:Ethylene Oxide / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D051381:Rats; D011916:Rats, Inbred F344; D014018:Tissue Distribution
C035018:N(7)-hydroxyethylguanine; D006147:Guanine; D004247:DNA; D005027:Ethylene Oxide