The localization and subcellular distribution of Trypanosoma cruzi nitric o
xide synthase was investigated in epimastigote cells by immunocytochemistry
at electron and light microscope level, using a polyclonal antibody to neu
ronal nitric oxide synthase, and also, at light microscope level, by the ni
cotinamide adenine dinucleotide phosphate-diaphorase histochemical reaction
. The immunoreactivity was ultrastructurally localized by electron microsco
py in the inner surface of cell membranes and in free cytosolic clusters in
the body, flagellum and apical extreme. Light microscopy showed that immun
oprecipitates, specific for the Trypanosoma cruzi nitric oxide synthase, co
-localized with the formazan precipitates generated by the diaphorase react
ion in the same areas identified by electron microscopy. These results, tak
en together with previous finding from our laboratory could help to explain
the involvement of the nitric oxide transduction pathway in T. cruzi epima
stigote motility.