title: Oxygen-dependent chemical tumorigenesis in a Nicotiana hybrid: inhibition by ascorbic acid and dinitrophenol.
abstract: Aqueous solutions of molecular oxygen, per se, or in combination with either pyrogallol or 6-azauracil increased tumorigenesis in Nicotiana suaveolens X Nicotiana langsdorffii seedlings relative to control seedlings. The biological activities of the organic chemicals were O2-dependent, because the substitution of N2 or O2 or the degassing of 0.1-1 mM solutions of the compounds eliminated or greatly reduced their tumorigenic effects. Rates of tumorigenesis exceeded 95% for 0.5 mM solutions of either pyrogallol or 6-azauracil solutions in the presence of l mM O2. Although tumors developed in 20% of seedlings in the presence of 1 mM O2, alone, 4-5 times more tumors were induced by the organic chemical--O2-H2O systems. Dinitrophenol and ascorbic acid, compounds which affect cellular respiration or redox systems, strongly inhibited the chemically-mediated tumorigenesis. Dinitrophenol was equally effective at one-tenth of the molar concentrations of ascorbic acid that were required for the suppressions of oncogenesis. Dehydroascorbic acid was much less inhibitory than ascorbic acid.
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D010100:Oxygen / Q000633:toxicity*; D010941:Plant Tumors / Q000139:chemically induced*; D010947:Plants, Toxic; D011748:Pyrogallol / Q000633:toxicity*; D012639:Seeds / Q000187:drug effects; D014026:Nicotiana / Q000187:drug effects; D014498:Uracil / Q000031:analogs & derivatives* / Q000633:toxicity*
chemical_list: D004140:Dinitrophenols; D011748:Pyrogallol; D014498:Uracil; D001205:Ascorbic Acid; D010100:Oxygen