Time course of renal Na-K-ATPase, NHE3, NKCC2, NCC, and ENaC abundance changes with dietary NaCl restriction.
We have used peptide-directed antibodies to each major renal Na transporter and channel proteins to screen renal homogenates for changes in Na transporter protein expression after initiation of dietary NaCl restriction. After equilibration on a NaCl-replete diet (2.0 meq. 200 g body wt(-1). day(-1)), rats were switched to a NaCl-deficient diet (0.02 meq. 200 g body wt(-1). day(-1)). Na excretion fell to 25% of baseline levels on day 1, followed by a further decrease <4% of baseline levels on day 3, of NaCl restriction. The decreased Na excretion at day 1 occurred despite the absence of a significant increase in plasma aldosterone level or in the abundance of any of the major renal Na transporters. However, after a 1-day lag, plasma aldosterone levels increased in association with increases in abundances of three aldosterone-regulated Na transporter proteins: the thiazide-sensitive Na-Cl cotransporter (NCC), the alpha-subunit of the amiloride-sensitive epithelial Na channel (alpha-ENaC), and the 70-kDa form of gamma-ENaC. RNase protection assays of transporter mRNA levels revealed an increase in renal alpha-ENaC mRNA coincident with the increase in alpha-ENaC protein abundance. However, there was no change in NCC mRNA abundance, suggesting that the increase in NCC protein in response to dietary NaCl restriction was not a result of altered gene transcription. These results point to early regulatory processes that decrease renal Na excretion without an increase in the abundance of any Na transporter, followed by a late aldosterone-dependent response associated with upregulation of NCC and ENaC.
Masilamani
Shyama
S
Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1603, USA.
Wang
Xiaoyan
X
Kim
Gheun-Ho
GH
Brooks
Heddwen
H
Nielsen
Jakob
J
Nielsen
Soren
S
Nakamura
Kenzo
K
Stokes
John B
JB
Knepper
Mark A
MA
D000450:Aldosterone / Q000097:blood; D000818:Animals; D015153:Blotting, Western; D004039:Diet, Sodium-Restricted; D053503:Epithelial Sodium Channels; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D023282:Nuclease Protection Assays; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000652:urine; D015222:Sodium Channels / Q000096:biosynthesis* / Q000235:genetics; D049992:Sodium Chloride Symporters; D017673:Sodium Chloride, Dietary; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis* / Q000235:genetics; D028021:Sodium-Potassium-Chloride Symporters / Q000096:biosynthesis* / Q000235:genetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics; D064466:Solute Carrier Family 12, Member 1; D027981:Symporters / Q000096:biosynthesis* / Q000235:genetics
D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; C578716:Slc12a1 protein, rat; C000613387:Slc9a3 protein, rat; D015222:Sodium Channels; D049992:Sodium Chloride Symporters; D017673:Sodium Chloride, Dietary; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D027981:Symporters; D000450:Aldosterone; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase