Nitrofurantoin-stimulated proteolysis in human erythrocytes: a novel index of toxic insult by nitroaromatics.

Nitrofurantoin is an antimicrobial agent that causes nonimmune hemolytic anemia in susceptible populations and produces oxidant stress and cellular damage by mechanisms that differ from those associated with oxidants such as phenylhydrazine, which has been shown to stimulate proteolysis in red cells (Goldberg and Boches, 1982). Thus a study of the effects of nitrofurantoin on proteolysis in normal human red cells and red cell hemolysate has been conducted. Nitrofurantoin produced greater than a 3- and an approximately 5-fold increase in the rate of tyrosine release from red cells at 100 and 800 microM, respectively, compared with untreated red cells. In hemolysates nitrofurantoin also effectively increased proteolysis with a 2.4- and 4.0-fold increase in the rate of tyrosine release monitored at 100 and 800 microM, respectively, relative to controls. Stimulation of proteolysis by nitrofurantoin occurred linearly with time and with hematocrit over the range 5-25%. The rate of nitrofurantoin-stimulated proteolysis varied with glucose concentration in the incubation medium with a 2-fold increase in activity monitored between 2 and 10 mM glucose. Inhibitors of flavoprotein activity (electron transport), such as 2'-AMP and NADP, decreased nitrofurantoin-enhanced proteolysis in red cells to control levels, whereas methylene blue provided only a slight increase in proteolysis and an anaerobic environment (N2) stimulated significantly the rate of tyrosine production. Although N-acetylcysteine protected against the stimulation of proteolysis produced by 10 microM nitrofurantoin, this protective effect was diminished at higher concentrations of drug.(ABSTRACT TRUNCATED AT 250 WORDS)