Kohn, Andrea B.; Lea, Jeanne M.; Moroz, Leonid L.; Greenberg, Robert M.
Nitric oxide (NO) is synthesized enzymatically by nitric oxide synthase (NOS). Several
groups have previously presented evidence for NOS activity and immunoreactivity in several
parasitic platyhelminths, including schistosomes. Here, we use 4,5-diaminofluorescein-2
diacetate (DAF-2 DA), a fluorescent indicator of NO, to detect NO in living schistosomes. In
adult worms, DAF-2 fluorescence is found selectively in epithelial-like cells. Fluorescence
increases when worms are incubated in L-arginine, the precursor of NO synthesis, and decreases
dramatically in the presence of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME),
indicating that predicted NO release may be NOS-dependent, and that enzymatic NO signaling
pathways may play an important role in schistosome physiology.