Carbon dioxide has been reported to react with peroxynitrite (ONOO-), a strong oxidant and nitrating agent, to form an ON02C02-adduct, altering the reactivity characteristic of peroxynitrite. We found that bicarbonate (O-10 mM) caused a dose-dependent increase of up to 6-fold in the formation of 84troguanlne in calf-thymus DNA incubated with 0.1 mM peroxynitrite, whereas it produced no apparent effect on Soxoguanine formation. In contrast, bicarbonate inhibited peroxynitrite-induced strand breakage in plasmid pBR322 DNA and thymine-propenal formation from thymidine. We conclude that CO#ICO~-reacts with peroxynitrite to form a potent nitrating agent, but also to inactivate hydroxyl-radicallike activity of peroxynitrous acid.

No abstract

No abstract

Cigarette smoking is a major cause of human cancer at a variety of sites, although its carcinogenic mechanisms remains unestablished. Cigarette smoke can be divided into two phases, gas phase and particulate matter (tar). Both phases contain high concentrations of oxidants and free radicals, especially nitric oxide (NO) and nitrogen oxides in the gas phase and quinone/hydroquinone complex in the tar. We have found that incubation of pBR322 plasmid DNA with aqueous extracts of cigarette tar and a NO-releasing compound (diethylamine NONOate) caused synergistic induction of DNA single-strand breakage, whereas either cigarette tar alone or NO alone induced much less strand breakage. This synergistic effect of cigarette tar and NO on DNA strand breakage was prevented by high concentrations of superoxide dismutase, carboxy-PTIO (an NO-trapping agent) or N-acetylcysteine, whereas hydroxyl radical scavengers such as dimethylsulfoxide, ethanol and D-mannitol did not show inhibitory effects. Possible mechanisms for this synergistic effect mediated by cigarette tar and NO are proposed, including involvement of peroxynitrite, which is a strong oxidant and nitrating agent formed rapidly by the reaction between NO and O2.-. NO is present in the gas phase of smoke and may be formed by a constitutive or inducible NO synthase in the lung, whereas O2.- is generated by auto-oxidation of polyhydroxyaromatic compounds such as catechol and 1,4-hydroquinone present in cigarette tar. Thus, potent reactive species including peroxynitrite formed by the interaction between cigarette tar and NO may play an important role in smoking-related diseases including lung cancer.

Dietary fiber content, water-holding capacity, and binding of artificial colors, vitamin, and cholate were studied for 12 species of green, brown, and red algae. Hijiki contained higher soluble dietary fiber and some specimens of wakame had the highest amount of insoluble dietary fiber. High water-holding capacity of wakame seemed to be characteristic, ranging from 19 to 44 g/g dry seaweed. When samples were immersed in acid water to simulate the gastric pH condition, almost all water-holding capacity of seaweeds decreased. Settling volume in water was similar to water-holding capacity, and wakame had the higher values. Susabi-nori, suji-aonori, and some specimens of wakame showed a higher capacity to bind amaranth than other seaweeds. Erythrosine and rose Bengal bound by many seaweeds were higher than amaranth. Wakame sporophyll and hijiki showed the highest percent binding (42.7-45.6%) for thiamin, but Mitsuishi-kombu and susabi-nori showed the lowest binding (8.3-10.6%). Binding of sodi um cholate by susabi-nori was the highest (12.6-15.5%); over twice that bound by another seaweeds ex cept suji-aonori (9.7%). However Mitsuishi-kombu, ma-kombu and one hijiki had a lower binding capacity (0-2.6%).