“…Although a small Na + ,K + -ATPase activity had already been reported in S. mansoni homogenate (Nechay et al 1980), we initiated our studies by re-investigating this enzyme due to its importance for maintaining membrane potential, sodium gradient and, indirectly, intracellular calcium concentrations (Sweadner 1989). The presence of Na + , K + -ATPase activities with different sensitivity to ouabain in tegumental and carcass preparations (Noël & Soares de Moura 1986) and the characterization of two classes of [ 3 H]ouabain binding sites in the homogenate (Pardon & Noël 1994) let us propose the existence of more than one isoenzyme in this worm, just as in mammals.…”