RELEASE OF NITRIC-OXIDE DURING THE EXPERIMENTAL-INFECTION WITH TRYPANOSOMA-CRUZI

We analysed the production of nitric oxide (NO) intermediates by cells from BALB/c mice infected with either virulent (Tulahuen or RA) or av irulent (CA-1) strains of Trypanosoma cruzi. Peritoneal or spleen cell s from mice infected with T. cruzi released NO when incubated without further stimuli. Cells from mice during the acute stage of infection a ccumulated higher levels of inducible NO synthase mRNA and produced bo th, before and after lypopoly-saccharide stimulation, higher amounts o f No than cells from mice chronically infected with T. cruzi. NO synth esis showed similar kinetics in connection with all three strains of T . cruzi, but cells from mice inbred with the Tulahuen or RA strains re leased higher levels of IFN-gamma, an activator of the NO pathways, th an cells from mice infected with the CA-1 strain. In vivo administrati on of L-Ng-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of No synthase, increased the susceptibility of mice to T. cruzi. We conc lude that infection with T. cruzi induces NO production, and suggest t hat NO plays a role in the resistance against the parasite.