Ouabain-insensitive Na(+)-ATPase activity in Trypanosoma cruzi epimastigotes.
In the present paper, the presence of a ouabain-insensitive Na(+)-stimulated, Mg(2+)-dependent ATPase activity in T. cruzi epimastigotes CL14 clone and Y strain was investigated. The increase in Na+ concentration (from 5 to 170 mM), in the presence of 2 mM ouabain, increases the ATPase activity in a saturable manner along a rectangular hyperbola. The Vmax 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 mM 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 mM, 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.
Caruso-Neves
C
C
Laboratório de Fisiologia Renal, Universidade Federal do Rio de Janeiro, Brazil.
Einicker-Lamas
M
M
Chagas
C
C
Oliveira
M M
MM
Vieyra
A
A
Lopes
A G
AG
D000704:Analysis of Variance; D000818:Animals; D004789:Enzyme Activation; D005665:Furosemide / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity; D014349:Trypanosoma cruzi / Q000201:enzymology*
D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium