title: Comparative effects of superoxide anion and hydrogen peroxide on microsomal and cytosolic glutathione S-transferase activities of rat liver.
abstract: Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membrane proteins. In addition to their role in drug metabolism by conjugating electrophilic and lipophilic compounds with glutathione (GSH), these enzymes display multiple functions in cells, including antioxidant action. It has been generalized that reactive oxygen species (ROS) inhibit cytosolic GSTs and activate microsomal GSTs; some evidence shows, however, that different ROS-generating systems can inhibit microsomal GST activity. We therefore tested the effect of Fe3+/ascorbate, another ROS-generating system, on cytosolic and microsomal GST activities from rat liver cytosol and microsomes, respectively, and compared it to that of hydrogen peroxide (H2O2). We found that, while both agents displayed similar inhibitory effects on cytosolic GST activity, they promoted opposite effects on microsomal GST activity. Using specific antioxidant enzymes, we corroborated that the effect of Fe3+/ascorbate involves generation of O2(.-) without dismutation into H2O2. Since these ROS have physicochemical properties and redox potentials that are very distinct, their reactivity is different, and their oxidative action is likely to have different targets. We discuss how these properties are related with the oxidative potency of ROS, especially those of O2(.-) and H2O2.
authors.affiliation: Laboratory of Pharmacology and Toxicology, Department of Pharmacological and Toxicological Chemistry, School of Chemical and Pharmaceutical Sciences, Universidad de Chile, Sergio Livingstone Polhammer (ex-Olivos) 1007, Independencia, Santiago 8380492, Chile. mel@ciq.uchile.cl
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Letelier
authors.forename: Alfredo
authors.initials: A
authors.lastname: Molina-Berríos
authors.forename: Juan
authors.initials: J
authors.lastname: Cortés-Troncoso
authors.forename: José A
authors.initials: JA
authors.lastname: Jara-Sandoval
authors.forename: Andrea
authors.initials: A
authors.lastname: Müller
authors.forename: Paula
authors.initials: P
authors.lastname: Aracena-Parks
mesh_terms: D000818:Animals; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000494:pharmacology*
chemical_list: D016877:Oxidants; D017382:Reactive Oxygen Species; D013481:Superoxides; D006861:Hydrogen Peroxide; D005982:Glutathione Transferase