title: Modifying effects of a single injection of phenobarbital on the inhibitory action of benzo(a)pyrene on 3H-thymidine incorporation into various organs of the mouse.
abstract: The effects of the procarcinogen benzo(a)pyrene and the enzyme inducer phenobarbital on the DNA turnover in various organs of male C57BL mice were evaluated by measuring the incorporation of [6-3H]thymidine. When injected intraperitoneally 48 h before sacrifice, benzo(a)pyrene (28.8 mg/kg body weight) inhibited the incorporation of 3H-thymidine into the spleen, thymus, testis, and small intestine. A corresponding analysis with phenobarbital sodium (75 mg/kg b.w.) revealed reduced incorporation of 3H-thymidine into the pancreas (after 24 h) and bone marrow (after 72 h). The effects of combining benzo(a)pyrene and phenobarbital was examined by injecting the latter agent either 24 h before or after the polycyclic hydrocarbon. A previous injection of phenobarbital resulted in a potentiation of the inhibitory action of benzo(a)pyrene in the spleen. However, when phenobarbital was given after benzo(a)pyrene, there was a five-fold increase of the 3H-thymidine incorporation into the liver in comparison to the controls given vehicle. The demonstration that a single injection of phenobarbital has modifying effects on the 3H-thymidine incorporation both when administered alone and in combination with benzo(a)pyrene indicates that enzyme inducers may influence the outcome in genotoxicity tests.
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology*; D013154:Spleen / Q000187:drug effects / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism*; D013950:Thymus Gland / Q000187:drug effects / Q000378:metabolism
chemical_list: D001564:Benzo(a)pyrene; D013936:Thymidine; D010634:Phenobarbital