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Ouabain-insensitive Na+-ATPase activity of Malpighian tubules fromRhodnius prolixus

Authors
Publisher
Elsevier Inc.
Publication Date
Volume
119
Issue
4
Identifiers
DOI: 10.1016/s0305-0491(98)00057-1
Keywords
  • Furosemide-Sensitive
  • Atpase Activity
  • Malpighian Tubular Cells
Disciplines
  • Chemistry
  • Medicine

Abstract

Abstract 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.

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