title: Effects of phenelzine and hydralazine on hydrogen peroxide production and proteolysis in human red blood cells.
abstract: The ability of the therapeutic agents phenelzine (PZ) and hydralazine (HD) to stimulate the rate of protein degradation and H2O2 production in human red blood cells (RBC) was characterized. PZ- and HD-stimulated proteolysis, as monitored either by a fluorescence assay or by high-pressure liquid chromatography, occurred in a dose-, time- and hematocrit-dependent manner. The more potent PZ (0.5 mM), in RBC suspension or hemolysate, stimulated the rate of leucine release by 131 and 63%, respectively, whereas HD (1.0 mM) in RBC suspension or hemolysate produced increases of 133 and 66% in the rate of leucine release, respectively. PZ (0.75 mM) addition to red cells resulted in a rapid stimulation of H2O2 generation during the first hour of incubation, whereas HD (0.75 mM) addition to red cells produced a gradual increase in the rate of H2O2 production over 5 h of incubation. Substantial inhibition of PZ- and HD-stimulated proteolysis in RBC was observed with N-acetylcysteine, N-ethylmaleimide and the inhibitors of methemoglobin reduction, NADP and 2'AMP. In contrast, antioxidants dithiothreitol, dimethylthiourea, dimethyl sulfoxide and dimethylfuran had little effect on the rates of PZ- and HD-stimulated protein degradation. Western blot analysis demonstrated little change in the membrane-bound levels of the calcium-activated neutral protease calpain after incubation with PZ or HD. However, PZ- and HD-stimulated amino acid release was inhibited (approximately 30-50%) by the calcium chelator EGTA, suggesting a potential role for calcium-activated neutral protease and divalent metal cations in PZ- and HD-stimulated proteolysis.
authors.affiliation: Institute of Chemical Toxicology, Wayne State University, Detroit, Michigan.
authors.forename: M
authors.initials: M
authors.lastname: Runge-Morris
authors.forename: R F
authors.initials: RF
authors.lastname: Novak
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002154:Calpain / Q000097:blood; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004533:Egtazic Acid / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D016166:Free Radical Scavengers; D006801:Humans; D006830:Hydralazine / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000097:blood*; D010624:Phenelzine / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000494:pharmacology; D013268:Stimulation, Chemical
chemical_list: D001798:Blood Proteins; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D006830:Hydralazine; D004533:Egtazic Acid; D006861:Hydrogen Peroxide; D002154:Calpain; D010624:Phenelzine