title: Activation of dopamine D1-like receptors induces acute internalization of the renal Na+/phosphate cotransporter NaPi-IIa in mouse kidney and OK cells.
abstract: The Na(+)/phosphate cotransporter NaPi-IIa (SLC34A1) is the major transporter mediating the reabsorption of P(i) in the proximal tubule. Expression and activity of NaPi-IIa is regulated by several factors, including parathyroid hormone, dopamine, metabolic acidosis, and dietary P(i) intake. Dopamine induces natriuresis and phosphaturia in vivo, and its actions on several Na(+)-transporting systems such as NHE3 and Na(+)-K(+)-ATPase have been investigated in detail. Using freshly isolated mouse kidney slices, perfused proximal tubules, and cultured renal epithelial cells, we examined the acute effects of dopamine on NaPi-IIa expression and localization. Incubation of isolated kidney slices with the selective D(1)-like receptor agonists fenoldopam (10 microM) and SKF-38393 (10 microM) for 1 h induced NaPi-IIa internalization and reduced expression of NaPi-IIa in the brush border membrane (BBM). The D(2)-like selective agonist quinpirole (1 microM) had no effect. The D(1) and D(2) agonists did not affect the renal Na(+)/sulfate cotransporter NaSi in the BBM of the proximal tubule. Studies with isolated perfused proximal tubules demonstrated that activation of luminal, but not basolateral, D(1)-like receptors caused NaPi-IIa internalization. In kidney slices, inhibition of PKC (1 microM chelerythrine) or ERK1/2 (20 microM PD-098089) pathways did not prevent the fenoldopam-induced internalization. Inhibition with the PKA blocker H-89 (10 microM) abolished the effect of fenoldopam. Immunoblot demonstrated a reduction of NaPi-IIa protein in BBMs from kidney slices treated with fenoldopam. Incubation of opossum kidney cells transfected with NaPi-IIa-green fluorescent protein chimera shifted fluorescence from the apical membrane to an intracellular pool. In summary, dopamine induces internalization of NaPi-IIa by activation of luminal D(1)-like receptors, an effect that is mediated by PKA.
authors.affiliation: Institute of Physiology, Univ. of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland.
authors.forename: Desa
authors.initials: D
authors.lastname: Bacic
authors.forename: Paola
authors.initials: P
authors.lastname: Capuano
authors.forename: Michel
authors.initials: M
authors.lastname: Baum
authors.forename: Jianning
authors.initials: J
authors.lastname: Zhang
authors.forename: Gerti
authors.initials: G
authors.lastname: Stange
authors.forename: Jürg
authors.initials: J
authors.lastname: Biber
authors.forename: Brigitte
authors.initials: B
authors.lastname: Kaissling
authors.forename: Orson W
authors.initials: OW
authors.lastname: Moe
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Heini
authors.initials: H
authors.lastname: Murer
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018491:Dopamine Agonists / Q000494:pharmacology; D015536:Down-Regulation; D004705:Endocytosis / Q000502:physiology; D018818:Fenoldopam / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008871:Microvilli / Q000378:metabolism; D009893:Opossums; D009924:Organ Culture Techniques; D019257:Quinpirole / Q000494:pharmacology; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters / Q000378:metabolism*
chemical_list: D018491:Dopamine Agonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; C493555:Slc34a1 protein, mouse; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters; D019257:Quinpirole; D017868:Cyclic AMP-Dependent Protein Kinases; D018818:Fenoldopam