Genotoxicity of Manufactured Gas Plant Residue (MGP) in Skin and Lung of Mice Following MGP Ingestion or Topical Administration

The DNA binding of manufactured gas plant residue (MGP) components in male B6C3F1 mice was investigated following oral and topical administration. Chemical-DNA adduct formation was evaluated for two MGP samples (Mix of 3 and Mix of 7) that varied in chemical composition. MGP (10 mg/200 μL acetone) was applied to the shaved backs of mice fitted with Elizabethan collars. Mice were sacrificed after 24 h and DNA was isolated from skin and lung. Mice were also maintained on gel diets containing 0.3% MGP. These mice were sacrificed after 28 days of diet administration and DNA was isolated from forestomach and lung. Chemical-DNA adduct formation was analyzed by 32P-postlabeling using TLC and HPLC. The Mix of 3 induced two times more DNA adducts in lung than the Mix of 7, following topical administration or ingestion. Topical administration of MGP resulted in a single major adduct in skin and a total of three adducts (two major and one minor) in lung. In contrast, ingestion of MGP resulted in lung DNA adduct profiles much less distinct than that observed following MGP topical administration. One of the several minor adducts detected in lung, induced by MGP ingestion, could be attributed to benzo[a]pyrene.