Distribution of nitric oxide synthase immunoreactivity in the nervous system and peripheral tissues of Schistosoma mansoni

The distribution of nitric: oxide synthase (NOS) immunoreactivity and putat ive NOS activity in adult Schistosoma mansoni was analysed using 3 differen t types of NOS antibodies and NADPH-diaphorase histochemistry. Although pot ential involvement of the gaseous radical nitric oxide (NO) in host respons e to infection by schistosomes has been suggested, there is little or no in formation available regarding the role, or even the presence, of the NO pat hway in schistosomes themselves. Here, we demonstrate that antibodies again st neuronal NOS (nNOS) and inducible NOS (iNOS) isoforms stain adult worms with distinctive patterns; anti-endothelial NOS (eNOS) shows no selective l abelling, nNOS-like immunoreactivity is found ill the main nerve cords and the peripheral nervous system. Putative sensor? neurons with apical neurona l processes leading to the tegument of male worms are also immunoreactive f or nNOS. Anti-iNOS labels a variety of predominantly nun-neuronal tissues, showing intense labelling at or near the surface of the worm and in compone nts of the gastrointestinal tract. The distribution of NADPH-diaphorase rea ctivity (a histochemical marker of NOS), is generally similar to the patter n of NOS immunoreactivity, including labelling of neuronal-like cells as we ll as developing eggs. These results suggest that an NOS-like enzyme is pre sent in S. mansoni, and indicate potential roles for the different NOS isof orms in neuronal signalling, reproduction and development.