MAINSTREAM AND SIDESTREAM CIGARETTE SMOKE-INDUCED DNA ADDUCTS IN C7B1AND DBA MICE

Exposure to environmental tobacco smoke (ETS), which is largely compos ed of the sidestream cigarette smoke, has been implicated in increased incidence of cancer among nonsmokers The present study was conducted to compare the potential of mainstream and sidestream cigarette smoke to induce DNA adducts in mice. Groups of female C57Bl and DBA mice wer e exposed twice daily for 65-70 weeks to mainstream or sidestream smok e from the University of Kentucky reference cigarettes (2R1) in a nose -only exposure system. Animals received a total particulate matter dos e of about 16 and 6 mg/kg body weight/exposure and exhibited blood car boxyhemoglobin levels of about 16 and 34%, for mainstream and sidestre am smoke-exposed groups, respectively. Pulmonary aryl hydrocarbon hydr oxylase (AHH) activity was induced by about 2- to 3-fold in both mains tream and sidestream groups of C57Bl and in mainstream smoke-exposed g roup of DBA mice, but not in sidestream smoke-exposed DBA mice. An ana lysis of total DNA adduct levels by the P-32-postlabeling assay showed a significant (12- to 25-fold) increase in the magnitude of preexisti ng lung DNA adducts in both mainstream and sidestream smoke-exposed C5 7Bl and DBA mice. Smoke exposures did not affect the total preexisting DNA adducts in liver of either strain. It is concluded that both main stream and sidestream smoke are capable of enhancing preexisting DNA a dducts in the lungs of chronically smoke-exposed mice.