Persistence of 7-(2-hydroxyethyl)guanine-DNA adducts in rats exposed to ethene by inhalation

Quantification of 7-(2-hydroxyethyl)guanine (7-HEG) adduct in DNA of livers and lymphocytes of male Sprague-Dawley rats exposed to 300 ppm ethene by inhalation (12 h a day for three consecutive days) was performed to evaluate the potential of ethene to produce DNA adducts in these tissues. The persistence of 7-HEG in livers and lymphocytes was studied in rats sacrificed 0, 1, 5, and 20 days after the last exposure, DNA samples from control and treated animals were analysed for 7-HEG and 7-methylguanine (7-MG) adducts by thin-layer chromatography (TLC) combined with a high pressure liquid chromatography (HPLC) assay, After a 8-day exposure to ethene, 7-HEG accumulated to a similar extent in liver and lymphocytes, with the mean adduct level of 7.0 +/- 0.7 adducts per 10(7) nucleotides in liver and 7.4 +/- 0.7 adducts per 10(7) nucleotides in lymphocytes of rats sacrificed immediately after cessation of exposure. The approximate half-life of 7-HEG was 5 days in liver and 3 days in lymphocytes, which is consistent with the loss of adduct primarily by spontaneous depurination. In addition, the background levels of 7-HEG and 7-MG were determined in the liver and lymphocytes from the control rats.