title: DNA methylation, cell proliferation, and histopathology in rats following repeated inhalation exposure to dimethyl sulfate.
abstract: Dimethyl sulfate (DMS) is an alkylating agent that is carcinogenic to the respiratory tract of rodents. DNA adducts, cell proliferation, and histopathology were assessed in rats to better understand the molecular dosimetry and tissue dynamics associated with repeated inhalation exposure to DMS. For DNA methylation, rats were exposed to DMS vapor 6 h/day for up to 10 days to 0.0, 0.1, 0.7 and 1.5 ppm. N7-Methylguanine and N3-methyladenine were detected in neutral thermal hydrolysates of DNA isolated from respiratory tract tissues by high-performance liquid chromatography (HPLC) using fluorescence and ultraviolet (UV) detection. DNA methylation was greatest in DNA isolated from nasal respiratory mucosa, less in olfactory, and little was found in lung. N7-Methylguanine levels in respiratory mucosa approached steady-state levels by day 5, and N7-methylguanine persistence following exposure for 5 consecutive days was also determined. Loss of N7-methylguanine from respiratory and olfactory mucosa appeared to follow first-order kinetics. N3-Methyladenine levels were at or below detection limits in all samples. The effect of DMS on histopathology and cell proliferation in the nasal epithelium was also investigated. Rats were exposed nose-only for 2 wk to DMS vapor at concentrations of 0, 0.1, 0.7, or 1.5 ppm. Inhalation exposure to DMS induced degenerative and inflammatory changes in nasal epithelium at >or=0.7 ppm. Cell proliferation evaluations showed a trend towards an increased response at 1.5 ppm. These experiments demonstrate that DMS can induce cytotoxic and proliferative effects and is a potent methylating agent of the nasal mucosa in vivo. These experiments will provide data for the development of dosimetry models useful for risk extrapolation.
authors.affiliation: Haskell Laboratory for Health and Environmental Sciences, E. I. du Pont de Nemours and Company, Newark, Delaware 19714-0050, USA.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Mathison
authors.forename: S Randall
authors.initials: SR
authors.lastname: Frame
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Bogdanffy
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism; D000280:Administration, Inhalation; D000477:Alkylating Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D004247:DNA / Q000378:metabolism; D018736:DNA Adducts / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D008745:Methylation; D008954:Models, Biological; D009153:Mutagens / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*; D009831:Olfactory Mucosa / Q000473:pathology; D011687:Purines / Q000378:metabolism; D051381:Rats; D012306:Risk; D013463:Sulfuric Acid Esters / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D000477:Alkylating Agents; D018736:DNA Adducts; D009153:Mutagens; D011687:Purines; D013463:Sulfuric Acid Esters; C025946:3-methyladenine; D006147:Guanine; C008450:7-methylguanine; D004247:DNA; D000225:Adenine; C007482:dimethyl sulfate