Long-term regulation of ENaC expression in kidney by angiotensin II.
We carried out semiquantitative immunoblotting of kidney to identify apical sodium transporter proteins whose abundances are regulated by angiotensin II. In NaCl-restricted rats (0.5 mEq Na/200 g BW/d), the type 1 angiotensin II receptor (AT1 receptor) antagonist, candesartan, (1 mg/kg of body weight per day SC for 2 days) markedly decreased the abundance of the alpha subunit of the epithelial sodium channel (ENaC). This subunit has been shown to be rate-limiting for assembly of mature ENaC complexes. In addition, systemic infusion of angiotensin II increased alphaENaC protein abundance in rat kidney cortex. The decrease in alphaENaC protein abundance in response to AT1 receptor blockade was associated with a fall in alphaENaC mRNA abundance (real-time RT-PCR), consistent with transcriptionally mediated regulation. The effect of AT1 receptor blockade on alphaENaC expression was not blocked by spironolactone, suggesting a direct role of the AT1 receptor in regulation of alphaENaC gene expression. Candesartan administration was also found to increase the abundances of the beta and gamma subunits. The increase in beta and gammaENaC protein abundance was not associated with a significant increase in the renal abundances of the corresponding mRNAs, suggesting a posttranscriptional mechanism. Immunocytochemistry confirmed the increase in beta and gammaENaC protein abundance and demonstrated candesartan-induced ENaC internalization in collecting duct cells. The results support the view that the angiotensin II receptor regulates ENaC abundance, consistent with a role for angiotensin II in regulation of collecting duct function.
Beutler
Kathleen T
KT
Laboratory of Kidney and Electrolyte Metabolism, NHLBI, National Institutes of Health, Bethesda, Md 20892-1603, USA.
Masilamani
Shyama
S
Turban
Sharon
S
Nielsen
Jakob
J
Brooks
Heddwen L
HL
Ageloff
Shana
S
Fenton
Robert A
RA
Packer
Randall K
RK
Knepper
Mark A
MA
D000804:Angiotensin II / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D001581:Benzothiadiazines; D001639:Bicarbonates / Q000097:blood; D001713:Biphenyl Compounds; D004232:Diuretics; D053503:Epithelial Sodium Channels; D005786:Gene Expression Regulation / Q000187:drug effects; D015151:Immunoblotting; D007260:Infusion Pumps; D007279:Injections, Subcutaneous; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism; D007686:Kidney Tubules, Distal / Q000187:drug effects / Q000378:metabolism; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D011188:Potassium / Q000652:urine; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000652:urine; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology; D049992:Sodium Chloride Symporters; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage; D013148:Spironolactone / Q000494:pharmacology; D027981:Symporters / Q000378:metabolism; D013777:Tetrazoles / Q000494:pharmacology; D013997:Time Factors
D057911:Angiotensin Receptor Antagonists; D001562:Benzimidazoles; D001581:Benzothiadiazines; D001639:Bicarbonates; D001713:Biphenyl Compounds; D004232:Diuretics; D053503:Epithelial Sodium Channels; D000451:Mineralocorticoid Receptor Antagonists; D021122:Protein Subunits; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D015222:Sodium Channels; D049993:Sodium Chloride Symporter Inhibitors; D049992:Sodium Chloride Symporters; D017673:Sodium Chloride, Dietary; D027981:Symporters; D013777:Tetrazoles; D000804:Angiotensin II; D013148:Spironolactone; D011188:Potassium; C081643:candesartan