Leishmania amazonensis: Characterization of an ouabain-insensitive Na+-ATPase activity

We characterized ouabain-insensitive Na+-ATPase activity present in the plasma membrane of Leishmania amazonensis and investigated its possible role in the growth of the parasite. An increase in Na+ concentration in the presence of 1 mM ouabain, increased the ATPase activity with a Vmax of 154.1 ± 13.5 nmol Pi × h−1 × mg−1 and a K0.5 of 28.9 ± 7.7 mM. Furosemide and sodium orthovanadate inhibited the Na+-stimulated ATPase activity with an IC50 of 270 μM and 0.10 μM, respectively. Furosemide inhibited the growth of L. amazonensis after 48 h incubation, with maximal effect after 96 h. The IC50 for furosemide was 840. On the other hand, ouabain (1 mM) did not change the growth of the parasite. Taken together, these results show that L. amazonensis expresses a P-type, ouabain-insensitive Na+-ATPase that could be involved with the growth of the parasite.