title: Flow regulation of collecting duct endothelin-1 production.
abstract: Collecting duct (CD) endothelin-1 (ET-1) is an important autocrine inhibitor of CD Na(+) reabsorption. Salt loading is thought to increase CD ET-1 production; however, definitive evidence of this, as well as understanding of the mechanisms transducing this effect, is lacking. Tubule fluid flow increases in response to Na(+) loading; hence, we studied flow modulation of CD ET-1 production. Three days of a high-salt diet increased mouse and rat inner medullary CD (IMCD) ET-1 mRNA expression. Acute furosemide infusion increased urinary ET-1 excretion in anesthetized rats. Primary cultures of mouse or rat IMCD detached in response to flow using a closed perfusion chamber, consequently a CD cell line (mpkCCDcl4) was examined. Flow increased ET-1 mRNA at shear stress rates exceeding 1 dyne/cm(2), with the maximal effect seen between 2 and 10 dyne/cm(2). Induction of ET-1 mRNA was first evident after 1 h, and most apparent after 2 h, of flow. Inhibition of calmodulin or dihydropyridine-sensitive Ca(2+) channels did not alter the flow response; however, chelation of intracellular Ca(2+) or removal of extracellular Ca(2+) largely prevented flow-stimulated ET-1 mRNA accumulation. Downregulation of protein kinase C (PKC) using phorbol 12-myristate 13-acetate, or PKC inhibition with calphostin C, markedly reduced flow-stimulated ET-1 mRNA levels. Flow-stimulated ET-1 mRNA accumulation was abolished by inhibition of phospholipase C (PLC). Taken together, these data indicate that flow increases CD ET-1 production and this is dependent on extracellular and intracellular Ca(2+), PKC, and PLC. These studies suggest a novel pathway for coupling alterations in extracellular fluid volume to CD ET-1 production and ultimately control of CD Na(+) reabsorption.
authors.affiliation: Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah; and Vascular Biology Center, Medical College of Georgia, Augusta, Georgia, USA.
authors.forename: Brianna
authors.initials: B
authors.lastname: Lyon-Roberts
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Strait
authors.forename: Evan
authors.initials: E
authors.lastname: van Peursem
authors.forename: Wararat
authors.initials: W
authors.lastname: Kittikulsuth
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Pollock
authors.forename: David M
authors.initials: DM
authors.lastname: Pollock
authors.forename: Donald E
authors.initials: DE
authors.lastname: Kohan
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D012982:Sodium, Dietary / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D019332:Endothelin-1; D017466:Receptors, Endothelin; D049994:Sodium Potassium Chloride Symporter Inhibitors; D012982:Sodium, Dietary; D005665:Furosemide; D012964:Sodium; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002118:Calcium