Ouabain-Insensitive Na+-ATPase Activity in Trypanosoma cruzi Epimastigotes

Abstract

In the present paper, the presence of a ouabain-insensitive Na+-stimulated, Mg2+-dependent ATPase activity in T. cruzi epimastigotes CL14 clone and Y strain was investigated. The increase in Na+ concentration (from 5 to 170 mᴍ), in the presence of 2 mᴍ ouabain, increases the ATPase activity in a saturable manner along a rectangular hyperbola. The was 18.0 ± 1.0 and 21.1 ± 1.1 nmoles Pi x mg-1 x min-1 and the half-activation value (K50) for Na+ was 34.3 ± 5.8 mᴍ and 37.7 ± 5.3 in CL14 clone and in Y strain, respectively. The Na+-stimulated ATPase activity was inhibited by 5-[aminosulfonyl]-4-chloro-2-[(2-furanylmethyl)-amino] benzoic acid (furosemide) in a dose-dependent manner. The half-inhibition value (I50) was 0.22 ± 0.03 and 0.24 ± 0.07 mᴍ, and the Hill number (n) was 0.99 ± 0.2 and 2.16 ± 0.29 for CL14 clone and Y strain, respectively. These data indicate that both cell types express the ouabain-insensitive Na+-ATPase activity, which might be considered the bio­chemical expression of the second Na+ pump