RESUMO
The blood dwelling stages of schistosomes have acetylcholinesterase (AChE) and nicotinic-like acetylcholine receptors (nAChR) on their teguments. Both AChE and nAChR are concentrated on the dorsal surface of the adult male, a major surface for nutrient uptake for the worm pair. Exposure of tegumental AChE and nAChR to acetylcholine (ACh), the natural ligand of these molecules, has a consequence for the transporting function of this membrane in some schistosome species. The rate of glucose uptake in vitro by Schistosoma haematobium and Schistosoma bovis adult worm pairs was enhanced by approximately 60% at blood concentrations of ACh. Schistosoma mansoni did not show a similar response. The specificity of the ACh interaction with nAChR and AChE was shown by ablation of the effect with specific antagonists of nAChR (d-tubocurarine and alpha-bungarotoxin) and an inhibitor of AChE (BW284C51). The primary effect occurs on the tegument since alpha-bungarotoxin and BW284C51 do not penetrate the schistosome tegument. The species differences in reliance on this mechanism are consistent with their relative sensitivities to the AChE inhibitory drug, metrifonate.