title: Subapical localization of the dopamine D3 receptor in proximal tubules of the rat kidney.
abstract: The dopamine D3 receptor (D3R), intensively studied in neuroscience, also plays an important role in the regulation of renal and cardiovascular function. In contrast to functional findings, less information is available on its localization in the kidney. Neither RT-PCR studies nor radioligand binding assays are suitable to selectively determine the distribution of renal D3R at the level of cellular or even subcellular structures. We studied the renal D3R distribution in Sprague-Dawley rats by a polyclonal antiserum directed against an epitope in the third intracytoplasmic loop. D3R immunoreactivity was detected by indirect immunofluorescence and confocal laser scanning microscopy. D3R staining was confined to the renal cortex and occurred in proximal convoluted tubules near or in direct connection with the urinary pole of the glomeruli. The fluorescent spots were restricted to the subapical portion of the proximal tubular cells. Double staining with the F-actin marker phalloidin revealed a localization of the D3R below the brush border region. However, staining by anti-beta1/beta2-adaptins, recognizing clathrin-coated compartments, did not correspond to the distribution of the D3R signal. This is the first description of a D3R accumulation in a cytoplasmic pool in the kidney, probably corresponding to a recycling mechanism or storage compartment.
authors.affiliation: Dept. of Pharmacology and Toxicology, Faculty of Medicine, University of Tübingen, Wilhelmstr. 56, D-72074 Tübingen, Germany.
authors.forename: Asja
authors.initials: A
authors.lastname: Nürnberger
authors.forename: Marcus
authors.initials: M
authors.lastname: Räbiger
authors.forename: Andreas
authors.initials: A
authors.lastname: Mack
authors.forename: Jorge
authors.initials: J
authors.lastname: Diaz
authors.forename: Pierre
authors.initials: P
authors.lastname: Sokoloff
authors.forename: Bernd
authors.initials: B
authors.lastname: Mühlbauer
authors.forename: Gerd
authors.initials: G
authors.lastname: Luippold
mesh_terms: D000818:Animals; D005455:Fluorescent Antibody Technique; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D050637:Receptors, Dopamine D3
chemical_list: C493595:Drd3 protein, rat; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3