Ouabain-insensitive Na(+)-ATPase activity of Malpighian tubules from Rhodnius prolixus.
In the present paper, we show the existence of a furosemide-sensitive Na(+)-stimulated, Mg(2+)-dependent ATPase activity in cell lysates of Malpighian tubular cells from Rhodnius prolixus, which could be the biochemical expression of the Na(+)-pump. The main characteristics of this activity are: (1) K0.5 for Na+ = 1.49 +/- 0.18 mM, (2) Vmax = 2.8 +/- 0.1 nmol inorganic orthophosphate (Pi).mg prot-1.min-1, (3) it is fully abolished by 2 mM furosemide, (4)it is insensitive to ouabain concentrations up to 10(-2) M, (5) it is sensitive to the presence of vanadate in the incubation medium indicating it to be a P-type ATPase, and (6) it is stimulated by nanomolar concentrations of Ca2+ in the incubation medium.
Caruso-Neves
C
C
Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, Brazil.
Meyer-Fernandes
J R
JR
Saad-Nehme
J
J
Proverbio
F
F
Marín
R
R
Lopes
A G
AG
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D027682:Cation Transport Proteins; D004789:Enzyme Activation / Q000502:physiology; D005665:Furosemide / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008317:Malpighian Tubules / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology*; D012239:Rhodnius / Q000201:enzymology*; D012964:Sodium / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D027682:Cation Transport Proteins; D014638:Vanadates; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D008274:Magnesium; D002118:Calcium