The relationship between tegumental disruption and muscle contraction in Schistosoma mansoni exposed to various compounds.

The antischistosomal drugs praziquantel and Ro 11-3128, which cause a tetanic contraction of Schistosoma musculature, concurrently produce a disruption of the parasite's tegument. Both phenomena are attenuated by preincubation of the parasites in high Mg2+ containing media before addition of the drugs, and the therapeutically inactive stereoisomers of these drugs cause neither effect. Other antischistosomal drugs tested cause neither muscle contraction nor tegumental disruption. Some unrelated agents which cause muscle contraction (but have no antischistosomal effect) alter the parasite's tegument, while others do not. Cytochalasin B, but not colchicine, causes tegumental disruption without affecting muscle tension. Thus, there is no simple correlation between a drug's antischistosomal activity or ability to contract the parasite's muscle and its ability to damage the parasite's tegument.