PT - JOURNAL ARTICLE AU - M Runge-Morris AU - R F Novak TI - Effects of phenelzine and hydralazine on hydrogen peroxide production and proteolysis in human red blood cells. DP - 1993 Dec 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 1401--1406 VI - 267 IP - 3 4099 - http://jpet.aspetjournals.org/content/267/3/1401.short 4100 - http://jpet.aspetjournals.org/content/267/3/1401.full SO - J Pharmacol Exp Ther1993 Dec 01; 267 AB - 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.