Adenylate cyclase in adults and cercariae of Schistosoma mansoni

Adenylate cyclase of adult Schistosoma mansoni is activated by serotonin (5-hydroxytryptamine). Serotonin activation is markedly enhanced by GTP. The poorly hydrolyzed analogs of GTP, guanylyl imidophosphate (Gpp(NH)p) and guanosine 5′-(3-O-thio)triphosphate activate the schistosome cyclase in the absence of serotonin. The activating effect of these nucleotides is increased in the presence of serotonin. Female adult schistosomes have only 40% as much NaF-stimulated activity as do the male parasites. In addition, the serotonin stimulation of adenylate cyclase in the females is only 20% as much as the males. Maximal activation of adenylate cyclase with NaF reveals that the adult parasites have tenfold higher activity than the cercariae. Cercarial adenylate cyclase shows very poor response to serotonin in the presence of GTP. Serotonin caused more significant activation of cercarial adenylate cyclase in the presence of guanylyl imidophosphate.