title: Epidermal growth factor inhibits amiloride-sensitive sodium absorption in renal collecting duct cells.
abstract: The effects of the ERK pathway on electrogenic transepithelial Na(+) absorption by renal collecting duct cells were determined. Approximately 90% of the unstimulated short-circuit current (15 +/- 1 microA/cm(2), n = 10) across conditionally immortalized murine collecting duct epithelial cells (mCT1) is amiloride sensitive and is likely mediated by apical epithelial Na(+) channels. Chronic exposure (24 h) of the epithelial monolayers to either EGF (50 ng/ml) or transforming growth factor-alpha (TGF-alpha; 20 ng/ml) reduced amiloride-sensitive short-circuit current by >60%. The inhibitory effect of EGF on Na(+) absorption was not due to inhibition of basolateral Na(+)-K(+)-ATPase, because the pump current elicited by permeabilization of apical membrane with nystatin was not reduced by EGF. Chronic exposure of the mCT1 cells to EGF (20 ng/ml, 24 h) elicited a 70-85% decrease in epithelial Na(+) channel subunit mRNA levels. Exposure of mCT1 cells to either EGF (20 ng/ml) or PMA (150 nM) induced rapid phosphorylation of p42/p44 (ERK1/2) and pretreatment of the monolayers with PD-98059 (an ERK kinase inhibitor; 30 microM) prevented phosphorylation of p42/p44. Similarly, pretreatment of mCT1 monolayers with PD-98059 prevented the EGF- and PMA-induced inhibition of amiloride-sensitive Na(+) absorption. The results of these studies demonstrate that amiloride-sensitive Na(+) absorption by renal collecting duct cells is regulated by the ERK pathway. This pathway may play a role in alterations in ion transport that occur in polycystic kidney disease.
authors.affiliation: Department of Pediatrics, Rainbow Center for Childhood PKD, Case Western Reserve University, Cleveland, Ohio 44106-4948, USA.
authors.forename: Jie-Pan
authors.initials: JP
authors.lastname: Shen
authors.forename: Calvin U
authors.initials: CU
authors.lastname: Cotton
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism; D004232:Diuretics / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D053503:Epithelial Sodium Channels; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D007690:Polycystic Kidney Diseases / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000235:genetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D002273:Carcinogens; D004232:Diuretics; D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D015222:Sodium Channels; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D000584:Amiloride; D012964:Sodium; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D013755:Tetradecanoylphorbol Acetate