title: Effects of genetic knock-down of organic anion transporter genes on secretion of fluorescent organic ions by Malpighian tubules of Drosophila melanogaster.
abstract: An earlier study has shown that RNAi knock-down of a single organic anion transporter (OAT) gene in the principal cells of Drosophila Malpighian tubules is associated with reductions in the expression of multiple, functionally related genes. In this study, we measured the rates of secretion of four fluorescent ions by tubules isolated from flies expressing targeted RNAi knock-down of specific OAT genes. Droplets secreted by isolated tubules set up in the Ramsay assay were collected in optically flat capillary tubes and the concentrations of fluorescent ions were determined by confocal laser scanning microscopy. Reductions in the expression of organic anion (OA) transporting polypeptide 58Dc (OATP; CG3380) were associated with reduced secretion of the OAs fluorescein and Texas Red. Reduction in the expression of Drosophila multidrug resistance associated protein (dMRP; CG6214) was correlated with reduced secretion of the P-glycoprotein substrate daunorubicin. Secretion of the organic cation quinacrine was unaffected by reduced expression of OATP, dMRP, or a multidrug efflux transporter (MET; CG30344). The results highlight the difficulties of assigning a rate-limiting role in transport of a specific OA to a single membrane transporter.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Chahine
authors.forename: Sara
authors.initials: S
authors.lastname: Seabrooke
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Donnell
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic; D003630:Daunorubicin; D004331:Drosophila melanogaster / Q000502:physiology*; D005260:Female; D019793:Fluorescein; D005456:Fluorescent Dyes; D055785:Gene Knockdown Techniques; D019450:Genes, MDR; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D008317:Malpighian Tubules / Q000378:metabolism*; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism*; D011796:Quinacrine; D014966:Xanthenes
chemical_list: D000903:Antibiotics, Antineoplastic; D005456:Fluorescent Dyes; D019476:Insect Proteins; D027361:Organic Anion Transporters; D014966:Xanthenes; C034657:Texas red; D011796:Quinacrine; D019793:Fluorescein; D003630:Daunorubicin