Reactions of (NO)-N-center dot,(NO2)-N-center dot and peroxynitrite in membranes: Physiological implications

Nitric oxide ((NO)-N-.) and nitrogen dioxide ((NO2)-N-.) are hydrophobic ga ses. Therefore, lipid membranes and hydrophobic regions of proteins are pot ential sinks for these species. In these hydrophobic environments, reactive nitrogen species will exhibit different chemistry than in aqueous environm ents due to higher local concentrations and the lack of hydrolysis reaction s. The peroxynitrite anion (ONOO-) and peroxynitrous acid (ONOOH) can freel y pass through lipid membranes, making peroxynitrite-mediated reactions in a hydrophobic environment also of extreme relevance. The reactions observed by these reactive nitrogen species in a hydrophobic milieu include oxidati on, nitration and even potent chain-breaking antioxidant reactions. The phy siological and toxicological relevance of these reactions is discussed.