Uremic concentrations of guanidino compounds inhibit neutrophil superoxideproduction

Background. In uremia, diminished reactive oxygen intermediate (ROI) produc tion is an important consequence of impaired neutrophil function. We have s tudied the effect of guanidino compounds, known uremic toxins, on neutrophi l ROI production in vitro. Methods. Neutrophils from healthy volunteers were exposed for three hours t o individual or mixed guanidino compounds (GC(mix)) at concentrations encou ntered in uremic plasma. After removal of guanidino compounds, neutrophils were activated by adhesion, N-formyl-methionyl-leucyl-phenyalanine (fMLP), phorbol 12-myristate 13-acetate (PMA), or opsonized zymosan, and superoxide : production was measured by lucigenin chemilumineseence (CL). The direct e ffect of guanidino compounds on superoxide production in activated neutroph ils was also measured. The energy status (ATP and creatine phosphate), anti oxidant status (total glutathione), and glycolytic flux (lactate production ) were measured. Results. The GC(mix) pretreatment decreased the superoxide production in ac tivated neutrophils (fMLP or zymosan) by 50% (P < 0.01) and the ATP concent ration by 60% (P < 0.05), and it inhibited glycolytic flux (lactate product ion) by 45% (P < 0.01), but did not alter glutathione concentration. Simult aneous exposure to GC(mix), and activation did not inhibit nicotinamide ade nine dinucleotide phosphate (NADPH) oxidase activity in cell lysates, but i nhibited superoxide formation in zymosan-activated intact neutrophils, and this inhibition was reversed following removal of the guanidino compounds. Conclusion. Guanidino-succinate, -propionate, and -butyrate were individual ly as potent as the GC(mix). Inhibition of neutrophil superoxide generation by guanidino compounds results from a depressed energy status. Uremic conc entrations of guanidino compounds significantly inhibit neutrophil metaboli sm, and this has serious implications for their function in host defense.