Use of the ramsay assay to measure fluid secretion and ion flux rates in the Drosophila melanogaster Malpighian tubule

Jeffrey N. Schellinger, Aylin R. Rodan

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Modulation of renal epithelial ion transport allows organisms to maintain ionic and osmotic homeostasis in the face of varying external conditions. The Drosophila melanogaster Malpighian (renal) tubule offers an unparalleled opportunity to study the molecular mechanisms of epithelial ion transport, due to the powerful genetics of this organism and the accessibility of its renal tubules to physiological study. Here, we describe the use of the Ramsay assay to measure fluid secretion rates from isolated fly renal tubules, with the use of ion-specific electrodes to measure sodium and potassium concentrations in the secreted fluid. This assay allows study of transepithelial fluid and ion fluxes of ~20 tubules at a time, without the need to transfer the secreted fluid to a separate apparatus to measure ion concentrations. Genetically distinct tubules can be analyzed to assess the role of specific genes in transport processes. Additionally, the bathing saline can be modified to examine the effects of its chemical characteristics, or drugs or hormones added. In summary, this technique allows the molecular characterization of basic mechanisms of epithelial ion transport in the Drosophila tubule, as well as regulation of these transport mechanisms.

Original languageEnglish (US)
Article numbere53144
JournalJournal of Visualized Experiments
Issue number105
StatePublished - Nov 25 2015


  • Cellular biology
  • Drosophila melanogaster
  • Epithelial ion transport
  • Fluid secretion
  • Ion-specific electrode
  • Issue 105
  • Malpighian tubule
  • Potassium flux
  • Ramsay assay
  • Renal physiology
  • Renal tubule
  • Sodium flux

ASJC Scopus subject areas

  • General Neuroscience
  • General Chemical Engineering
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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