Profiling of renal tubule Na+ transporter abundances in NHE3 and NCC null mice using targeted proteomics
HL Brooks, AM Sorensen, J Terris… - The Journal of …, 2001 - Wiley Online Library
The Journal of physiology, 2001•Wiley Online Library
1 The Na+‐H+ exchanger NHE3 and the thiazide‐sensitive Na+‐Cl− cotransporter NCC are
the major apical sodium transporters in the proximal convoluted tubule and the distal
convoluted tubule of the kidney, respectively. We investigated the mechanism of
compensation that allows maintenance of sodium balance in NHE3 knockout mice and in
NCC knockout mice. 2 We used a so‐called 'targeted proteomics' approach, which profiles
the entire renal tubule with regard to changes in Na+ transporter and aquaporin abundance …
the major apical sodium transporters in the proximal convoluted tubule and the distal
convoluted tubule of the kidney, respectively. We investigated the mechanism of
compensation that allows maintenance of sodium balance in NHE3 knockout mice and in
NCC knockout mice. 2 We used a so‐called 'targeted proteomics' approach, which profiles
the entire renal tubule with regard to changes in Na+ transporter and aquaporin abundance …
- 1The Na+‐H+ exchanger NHE3 and the thiazide‐sensitive Na+‐Cl− cotransporter NCC are the major apical sodium transporters in the proximal convoluted tubule and the distal convoluted tubule of the kidney, respectively. We investigated the mechanism of compensation that allows maintenance of sodium balance in NHE3 knockout mice and in NCC knockout mice.
- 2We used a so‐called ‘targeted proteomics’ approach, which profiles the entire renal tubule with regard to changes in Na+ transporter and aquaporin abundance in response to the gene deletions. Specific antibodies to the Na+ transporters and aquaporins expressed along the nephron were utilized to determine the relative abundance of each transporter. Semiquantitative immunoblotting was used which gives an estimate of the percentage change in abundance of each transporter in knockout compared with wild‐type mice.
- 3In NHE3 knockout mice three changes were identified which could compensate for the loss of NHE3‐mediated sodium absorption. (a) The proximal sodium‐phosphate cotransporter NaPi‐2 was markedly upregulated. (b) In the collecting duct, the 70 kDa form of the γ‐subunit of the epithelial sodium channel, ENaC, exhibited an increase in abundance. This is thought to be an aldosterone‐stimulated form of γ‐ENaC. (c) Glomerular filtration was significantly reduced.
- 4In the NCC knockout mice, amongst all the sodium transporters expressed along the renal tubule, only the 70 kDa form of the γ‐subunit of the epithelial sodium channel, ENaC, exhibited an increase in abundance.
- 5In conclusion, both mouse knockout models demonstrated successful compensation for loss of the deleted transporter. More extensive adaptation occurred in the case of the NHE3 knockout, presumably because NHE3 is responsible for much more sodium absorption in normal mice than in NCC knockout mice.
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