title: Extracellular cGMP inhibits transepithelial sodium transport by LLC-PK1 renal tubular cells.
abstract: Both atrial natriuretic peptide (ANP) and sodium nitroprusside (SNP) inhibit tubular sodium reabsorption by generation of guanosine 3',5'-cyclic monophosphate (cGMP). To determine the role of extracellular cGMP in this response, monolayers of porcine renal tubular LLC-PK1 cells were incubated for 5 min with ANP, SNP, cGMP, or 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) (10 nM to 0.1 mM). Transepithelial sodium transport was measured as amiloride-inhibitable short-circuit current (Isc). Incubation of cell monolayers with 1 microM of ANP, cGMP, or 8-BrcGMP inhibited Isc by > 70%, as did SNP at 100 microM (P < 0.01). Adenosine 3',5'-cyclic monophosphate (0.1 mM) had no significant effect. Incubation of monolayers with 1 microM LY-83583 (an inhibitor of guanylyl cyclase), 10 microM probenecid (an organic anion transport inhibitor), or preincubation with 1 microgram/ml nocodazole (a microtubule disrupter) reduced extracellular accumulation of cGMP (P < 0.05) and abolished the SNP-mediated reduction of Isc. However, addition of these inhibitors did not affect reduction of Isc by exogenous cGMP. We conclude that SNP inhibits sodium transport by LLC-PK1 monolayers through generation of cGMP but that extrusion of cGMP out the cell is necessary for its effect.
authors.affiliation: Department of Pediatrics, University of Virginia, Charlottesville 22908, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Chevalier
authors.forename: G D
authors.initials: GD
authors.lastname: Fang
authors.forename: M
authors.initials: M
authors.lastname: Garmey
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D001692:Biological Transport / Q000502:physiology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D004553:Electric Conductivity; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism*; D018374:LLC-PK1 Cells / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism* / Q000502:physiology; D013552:Swine
chemical_list: D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009320:Atrial Natriuretic Factor; D012964:Sodium; D006152:Cyclic GMP