title: Fluid reabsorption and ion transport by the lower Malpighian tubules of adult female Drosophila.
abstract: The properties of the Malpighian tubules of Drosophila melanogaster change along their length. The upstream main segments secrete K(+)-rich fluid at a high rate. From this, the lower tubules reabsorb significant amounts of water and K+. Under stimulation, K+ reabsorption is accelerated. In addition, the lower tubules acidify the fluid passed to them by the main segments and secrete Ca2+ into it, adding to that transported there by the upstream epithelium. In contrast to the lumen-positive transepithelial potential difference (TEP) of the main segments, the TEP in the lower tubules is much lower and becomes lumen-negative close to their downstream junction with the common ureter. We suggest that the role of the lower tubule is to reduce the flow of K(+)-rich fluid that passes to the hindgut; this allows the hindgut to process the flow of excretory fluid more thoroughly.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: O'Donnell
authors.forename: S H
authors.initials: SH
authors.lastname: Maddrell
mesh_terms: D000042:Absorption; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004331:Drosophila melanogaster / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D008317:Malpighian Tubules / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D011188:Potassium; D002118:Calcium