title: Renal Na/H exchanger NHE-3 and Na-PO4 cotransporter NaPi-2 protein expression in glucocorticoid excess and deficient states.
abstract: Administration of pharmacologic doses of glucocorticoid in vivo increases renal proximal tubule apical membrane Na/H exchange and decreases Na/PO4 cotransport activity (1). Current data suggest that the NHE-3 and NaPi-2 proteins mediate significant fractions of proximal tubule apical membrane Na/H exchange and Na/PO4 cotransport, respectively. This study examines whether glucocorticoid excess or deficiency affects NHE-3 and NaPi-2 protein abundance and the intrarenal distribution of these transporters. Protein abundance of NHE-3 and NaPi-2 in control rats was compared to rats rendered glucocorticoid-deficient by bilateral adrenalectomy, and to rats receiving pharmacologic doses of dexamethasone using immunoblots and immunohistochemistry. Adrenalectomy had modest effects on NHE-3 protein abundance, but dexamethasone administration to either adrenalectomized or sham-operated rats significantly increased NHE-3 protein abundance in both the proximal tubule and thick ascending limb, but not the thin descending limb. Adrenalectomy increased NaPi-2 protein abundance in the proximal tubule, whereas dexamethasone administration dramatically suppressed NaPi-2 protein on the apical membrane in both adrenalectomized and sham-operated animals. No significant reciprocal increase in subapical NaPi-2 staining was seen in the dexamethasone-treated rats. The present study shows that glucocorticoids regulate proximal tubule apical membrane Na/H exchange and NaPi cotransport by changes in protein abundance of NHE-3 and NaPi-2, respectively.
authors.affiliation: Department of Anatomy, University of Zürich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Loffing
authors.forename: M
authors.initials: M
authors.lastname: Lötscher
authors.forename: B
authors.initials: B
authors.lastname: Kaissling
authors.forename: J
authors.initials: J
authors.lastname: Biber
authors.forename: H
authors.initials: H
authors.lastname: Murer
authors.forename: M
authors.initials: M
authors.lastname: Seikaly
authors.forename: R J
authors.initials: RJ
authors.lastname: Alpern
authors.forename: M
authors.initials: M
authors.lastname: Levi
authors.forename: M
authors.initials: M
authors.lastname: Baum
authors.forename: O W
authors.initials: OW
authors.lastname: Moe
mesh_terms: D033963:Adaptor Protein Complex 3; D033966:Adaptor Protein Complex beta Subunits; D000315:Adrenalectomy; D000704:Analysis of Variance; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D004195:Disease Models, Animal; D005938:Glucocorticoids / Q000172:deficiency / Q000378:metabolism*; D015151:Immunoblotting; D007150:Immunohistochemistry; D007672:Kidney Cortex / Q000378:metabolism*; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters
chemical_list: C095597:AP3B2 protein, human; D033963:Adaptor Protein Complex 3; D033966:Adaptor Protein Complex beta Subunits; D002352:Carrier Proteins; D005938:Glucocorticoids; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C000613385:SLC9A3 protein, human; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters