Na transport in autosomal recessive polycystic kidney disease (ARPKD) cyst lining epithelial cells.
Autosomal dominant (ADPKD) and recessive (ARPKD) polycystic kidney disease are characterized by the progressive growth and expansion of cysts or ectatic collecting ducts, respectively, that ultimately destroy the normal renal parenchyma. Evidence from experimental models of ADPKD suggests that transepithelial Na and fluid secretion contribute to cyst growth, yet little is known about solute transport in ARPKD. This purpose of this study was to begin to characterize the expression and polarity of transport proteins involved in vectorial Na movement in ARPKD epithelium. Immunodetectable alpha1 and beta2 subunits of the Na/K-ATPase localized to the apical membrane of collecting duct cysts in tissue sections of human fetal ARPKD nephrectomy specimens and conditionally immortalized cells derived from these cysts. Measurements of transepithelial (22)Na transport performed on monolayers of ARPKD and age-matched collecting tubule (HFCT) cells grown on permeable supports revealed net Na absorption in both models. However, ARPKD cells absorbed Na at a rate approximately 50% greater than that of HFCT. Furthermore, Na absorption in ARPKD cells was partially inhibited by 100 micro M apical amiloride or 1 mM basolateral but not apical ouabain. Northern blot analyses of ARPKD whole kidney and Western immunoblot of ARPKD cells showed approximately twofold greater expression of the alpha-subunit of the epithelial Na channel (ENaC) compared with age-matched controls. These results suggest that, despite the presence of apical Na/K-ATPase, ARPKD cyst-lining cells absorb Na by a pathway that is modestly amiloride-sensitive. Whether Na absorption is mediated by ENaC, perhaps of nonclassical subunit composition, or another amiloride-sensitive transporter remains to be determined.
Rohatgi
Rajeev
R
Division of Renal Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA.
Greenberg
Andrew
A
Burrow
Christopher R
CR
Wilson
Patricia D
PD
Satlin
Lisa M
LM
D002352:Carrier Proteins / Q000378:metabolism; D018929:Cell Culture Techniques; D003560:Cysts / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D017136:Ion Transport; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D017044:Polycystic Kidney, Autosomal Recessive / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002352:Carrier Proteins; D015222:Sodium Channels; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase