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An unexpected role for angiotensin II in the link between dietary salt and proximal reabsorption.
- Source :
-
The Journal of clinical investigation [J Clin Invest] 2006 Apr; Vol. 116 (4), pp. 1110-6. Date of Electronic Publication: 2006 Mar 23. - Publication Year :
- 2006
-
Abstract
- We set out to confirm the long-held, but untested, assumption that dietary salt affects proximal reabsorption through reciprocal effects on the renin-angiotensin system in a way that facilitates salt homeostasis. Wistar rats were fed standard or high-salt diets for 7 days and then subjected to renal micropuncture for determination of single-nephron GFR (SNGFR) and proximal reabsorption. The tubuloglomerular feedback (TGF) system was used as a tool to manipulate SNGFR in order to distinguish primary changes in net proximal reabsorption (Jprox) from changes due to glomerulotubular balance. The influence of Ang II over Jprox was determined by the sensitivity of Jprox to the AT1 receptor antagonist, losartan. Plasma, whole kidneys, and fluid from midproximal tubules were assayed for Ang II content by radioimmunoassay. In rats on the standard diet, losartan reduced Jprox by 25% and reduced the maximum range of the TGF response by 50%. The high-salt diet suppressed plasma and whole-kidney Ang II levels. But the high-salt diet failed to reduce the impact of losartan on Jprox or the TGF response and actually caused tubular fluid Ang II content to increase. The persistent effect of Ang II on Jprox prevented a major rise in late proximal flow rate in response to the high-salt diet. These observations challenge the traditional model and indicate that the role of proximal tubular Ang II in salt-replete rats is to stabilize nephron function rather than to contribute to salt homeostasis.
- Subjects :
- Absorption physiology
Angiotensin II blood
Angiotensin II pharmacokinetics
Animals
Homeostasis
Kidney Tubules, Proximal metabolism
Male
Nephrons physiology
Rats
Rats, Wistar
Sodium, Dietary administration & dosage
Angiotensin II metabolism
Kidney Tubules, Proximal physiology
Sodium, Dietary metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9738
- Volume :
- 116
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- The Journal of clinical investigation
- Publication Type :
- Academic Journal
- Accession number :
- 16557296
- Full Text :
- https://doi.org/10.1172/JCI26092