Adrenergic regulation of salt and fluid secretion in human medullary collecting duct cells.
Transepithelial salt and fluid secretion mediated by cAMP in initial inner medullary collecting ducts (IMCDi) may be important for making final adjustments to urine composition. We examined in primary cultures of human IMCDi cells the effects of adrenergic receptor (AR) agonists and antagonists on intracellular cAMP levels, short-circuit current (I(SC)), and fluid secretion. Epinephrine (1 microM), norepinephrine (1 microM), and isoproterenol (10 nM) individually increased intracellular cAMP levels 57-, 2-, and 25-fold, respectively, and stimulated I(SC) 3.3-, 2.9-, and 3.4-fold, respectively. beta-AR activation increased net fluid secretion by cultured human IMCDi cell monolayers from 0.09 +/- 0.04 to 0.26 +/- 0.05 microl x h(-1) x cm(-2) and freshly isolated rat IMCDi from 0.02 +/- 0.01 to 0.09 +/- 0.02 nl x h(-1) x mm(-1). In monolayers, these effects were eliminated by blocking beta2-AR, but not beta1-AR. Activation of alpha2-AR with guanabenz inhibited isoproterenol-induced I(SC) by 37% in human IMCDi monolayers and fluid secretion by 91% in rat IMCDi. Immunohistochemistry of human medullary tissue sections revealed greater expression of beta2-AR than beta1-AR; beta2-AR was localized to the basolateral membranes of human IMCDi. Immunoblots identified alpha2A-AR and alpha2B-AR in cultured human IMCDi cell monolayers. We conclude that 1) catecholamines stimulate cAMP-dependent anion and fluid secretion by IMCDi cells primarily through beta2-AR activation and 2) alpha2-AR activation attenuates cAMP-dependent anion secretion.
Wallace
Darren P
DP
Kidney Institute, University of Kansas Medical Center, Kansas City, KS 66160, USA. dwallace@kumc.edu
Reif
Gail
G
Hedge
Anne-Marie
AM
Thrasher
J Brantley
JB
Pietrow
Paul
P
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D000838:Anions / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007679:Kidney Medulla / Q000166:cytology / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D012492:Salts / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000838:Anions; C505032:CFTR protein, human; D002712:Chlorides; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; C578877:SLC12A2 protein, human; D012492:Salts; C578879:Slc12a2 protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D009638:Norepinephrine; D004837:Epinephrine