title: Regulation of glomerulotubular balance. I. Impact of dopamine on flow-dependent transport.
abstract: In response to volume expansion, locally generated dopamine decreases proximal tubule reabsorption by reducing both Na/H-exchanger 3 (NHE3) and Na-K-ATPase activity. We have previously demonstrated that mouse proximal tubules in vitro respond to changes in luminal flow with proportional changes in Na(+) and HCO(3)(-) reabsorption and have suggested that this observation underlies glomerulotubular balance. In the present work, we investigate the impact of dopamine on the sensitivity of reabsorptive fluxes to changes in luminal flow. Mouse proximal tubules were microperfused in vitro at low and high flow rates, and volume and HCO(3)(-) reabsorption (J(v) and J(HCO3)) were measured, while Na(+) and Cl(-) reabsorption (J(Na) and J(Cl)) were estimated. Raising luminal flow increased J(v), J(Na), and J(HCO3) but did not change J(Cl). Luminal dopamine did not change J(v), J(Na), and J(HCO3) at low flow rates but completely abolished the increments of Na(+) absorption by flow and partially inhibited the flow-stimulated HCO(3)(-) absorption. The remaining flow-stimulated HCO(3)(-) absorption was completely abolished by bafilomycin. The DA1 receptor blocker SCH23390 and the PKA inhibitor H89 blocked the effect of exogenous dopamine and produced a two to threefold increase in the sensitivity of proximal Na(+) reabsorption to luminal flow rate. Under the variety of perfusion conditions, changes in cell volume were small and did not always parallel changes in Na(+) transport. We conclude that 1) dopamine inhibits flow-stimulated NHE3 activity by activation of the DA1 receptor via a PKA-mediated mechanism; 2) dopamine has no effect on flow-stimulated H-ATPase activity; 3) there is no evidence of flow stimulation of Cl(-) reabsorption; and 4) the impact of dopamine is a coordinated modulation of both luminal and peritubular Na(+) transporters.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06520-8026, USA.
authors.forename: Zhaopeng
authors.initials: Z
authors.lastname: Du
authors.forename: Qingshang
authors.initials: Q
authors.lastname: Yan
authors.forename: Laxiang
authors.initials: L
authors.lastname: Wan
authors.forename: Sheldon
authors.initials: S
authors.lastname: Weinbaum
authors.forename: Alan M
authors.initials: AM
authors.lastname: Weinstein
authors.forename: Tong
authors.initials: T
authors.lastname: Wang
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000465:Algorithms; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D005260:Female; D007546:Isoquinolines / Q000494:pharmacology; D007678:Kidney Glomerulus / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D051379:Mice; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors; D012964:Sodium / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D001552:Benzazepines; D001639:Bicarbonates; D002712:Chlorides; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007546:Isoquinolines; D018942:Macrolides; D017447:Receptors, Dopamine D1; C534628:SCH 23390; D013449:Sulfonamides; C057620:bafilomycin A; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013469:Sulpiride; D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases; D006180:Proton-Translocating ATPases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D004298:Dopamine