title: The roles of V-type H+-ATPase and Na+/K+-ATPase in energizing K+and H+transport in larval Drosophila gut epithelia.
abstract: We analyzed V-type H+-ATPase (VA) and Na+/K+-ATPase (NKA) along the caeca and midgut of third instar Drosophila larvae using immunohistochemistry and ATPase activity assays. Corresponding H+and K+fluxes were characterized using the Scanning Ion-Selective Electrode Technique (SIET), and the roles of transport ATPases in energizing ion transport across the larval gut were investigated by basal application of bafilomycin, a VA inhibitor, and ouabain, a NKA inhibitor. Addition of bafilomycin led to a decrease in H+absorption along the caeca and midgut except at the copper cells and large flat cell zone of the middle midgut. H+absorption was decreased by acetazolamide, consistent with carbonic anhydrase activity in all regions except at the large flat cell zone of the middle midgut. Bafilomycin or acetazolamide also led to decreased K+absorption across the caeca and the anterior midgut. Our data show the dependence of K+transport on H+gradients established by the VA in the latter regions, consistent with the presence of a Cation-Proton Antiporter (CPA2) identified in other insect epithelia. Addition of ouabain led to the increase of K+absorption along the anterior midgut and the large flat cell zone of the middle midgut, suggesting a role for the NKA in these regions. This study shows the importance of both ATPases in driving ion transport across the gut of larval Drosophila.
authors.affiliation: McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada. Electronic address: natalie.dsilva@gmail.com.
authors.forename: Natalie M
authors.initials: NM
authors.lastname: D'Silva
authors.affiliation: York University, 4700 Keele St, Toronto, ON M3J 1P3, Canada. Electronic address: adonini@yorku.ca.
authors.forename: Andrew
authors.initials: A
authors.lastname: Donini
authors.affiliation: McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada. Electronic address: odonnell@mcmaster.ca.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Donnell
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D004331:Drosophila melanogaster / Q000254:growth & development / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006859:Hydrogen / Q000378:metabolism; D019476:Insect Proteins / Q000378:metabolism*; D017136:Ion Transport; D017736:Ion-Selective Electrodes; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D019476:Insect Proteins; D010042:Ouabain; D006859:Hydrogen; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Drosophila melanogaster; Ion transport; Na(+)/K(+) ATPase; V-type H(+)-ATPase