Ouabain-insensitive Na +-ATPase activity of Malpighian tubules from Rhodnius prolixus

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 1998-04, Vol.119 (4), p.807-811
• Main Authors: Caruso-Neves, Celso, Meyer-Fernandes, José R, Saad-Nehme, Jorge, Proverbio, Fulgencio, Marı́n, Reinaldo, Lopes, Anı́bal G
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Animals; ATPase activity; Calcium - pharmacology; Cation Transport Proteins; Enzyme Activation - physiology; Furosemide - pharmacology; Furosemide-sensitive; Kinetics; Magnesium - pharmacology; Malpighian tubular cells; Malpighian Tubules - enzymology; Ouabain - pharmacology; Rhodnius - enzymology; Sodium - pharmacology; Vanadates - pharmacology
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/S0305-0491(98)00057-1

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) K 0.5 for Na +=1.49±0.18 mM, (2) V max=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 Ca 2+ in the incubation medium.