title: Stimulation of aquaporin-mediated fluid transport by cyclic GMP in human retinal pigment epithelium in vitro.
abstract: OBJECTIVE
  The retinal pigment epithelium (RPE) expresses aquaporin-1 (AQP1) and components of the natriuretic peptide signaling pathway. We hypothesized that stimulation of the natriuretic signaling pathway in RPE with atrial natriuretic peptide (ANP) and with membrane-permeable analogs of cGMP would induce a net apical-to-basal transport of fluid.
  
  
  METHODS
  The hypothesis was tested using human RPE cultures that retain properties seen in vivo. Confluent monolayers were treated with ANP or membrane-permeable cGMP analogs in the presence of anantin, H-8, and an AQP1 inhibitor, AqB013. Fluid movement from the apical to basal chambers was measured by weight and used to calculate net fluid transport.
  
  
  RESULTS
  Our results demonstrated a 40% increase in net apical-to-basal fluid transport by ANP (5 μM) that was inhibited completely by the ANP receptor antagonist anantin and a 60% increase in net apical-to-basal fluid transport in response to the extracellularly applied membrane-permeable cGMP analog pCPT-cGMP (50 μM), which was not affected by the protein kinase G inhibitor H-8. The aquaporin antagonist AqB013 (20 μM) inhibited the cGMP-stimulated RPE fluid flux.
  
  
  CONCLUSIONS
  The effect of cGMP is consistent with an enhancement of the net fluid flux in RPE mediated by AQP1 channels. Pharmacologic activation of cGMP signaling and concomitant stimulation of fluid uptake from the subretinal space could offer insights into a new approach to treating or reducing the risk of retinal detachment.
authors.affiliation: Department of Cell Biology & Anatomy, University of Arizona, Tucson, Arizona, USA.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Baetz
authors.forename: W Daniel
authors.initials: WD
authors.lastname: Stamer
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Yool
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009320:Atrial Natriuretic Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology; D001693:Biological Transport, Active; D015153:Blotting, Western; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism; D014867:Water / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C496020:AQP1 protein, human; C474799:CPT-cGMP; D007546:Isoquinolines; D010456:Peptides, Cyclic; D014867:Water; C068090:anantin; D051398:Aquaporin 1; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D009320:Atrial Natriuretic Factor; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP