Schistosoma mansoni: preparation, characterization of (Na+ + K+)ATPase from tegument and carcass

The preparation and some biochemical properties of a (Na+ + K+)ATPase from male adult Schistosoma mansoni are described. After incubation in a membrane disruption medium, the tegument and carcass of the worms were separated and treated to obtain fractions enriched in (Na+ + K+)ATPase. The activity of the tegumental ouabain sensitive (Na+ + K+)ATPase at 37 C was 20.3 mumole Pi X mg-1 protein X hr-1 and represented 32% of the total ATPase activity. The (Na+ + K+)ATPase prepared from the carcass had a lower specific activity (3.7 mumole Pi X mg-1 protein X hr-1) but a higher relative activity (55%). Similar concentrations of Na+ and K+ activated the enzymes from both sources, and both enzymes were inhibited by similar concentrations of calcium. However, the enzyme from carcass was ten times more sensitive to ouabain than the enzyme from tegument. Comparison with results obtained on the (Na+ + K+)ATPase of human heart showed that the enzymes from the worms were more resistant to ouabain. The half maximal inhibitory concentration of dihydroouabain compared to that of ouabain was also different in the enzymes from human and worm. We conclude that (1) there exists at least one structural difference between the (Na+ + K+)ATPase of S. mansoni and that of the human host, and (2) it is useful to separately study the enzymes from tegument and carcass because they differ in sensitivity to cardiac glycosides.