Effect of salt intake on afferent arteriolar dilatation: role of connecting tubule glomerular feedback (CTGF).
Am J Physiol Renal Physiol
; 313(6): F1209-F1215, 2017 Dec 01.
Article
em En
| MEDLINE
| ID: mdl-28835421
ABSTRACT
Afferent arteriole (Af-Art) resistance is modulated by two intrinsic nephron feedbacks 1) the vasoconstrictor tubuloglomerular feedback (TGF) mediated by Na+-K+-2Cl- cotransporters (NKCC2) in the macula densa and blocked by furosemide and 2) the vasodilator connecting tubule glomerular feedback (CTGF), mediated by epithelial Na+ channels (ENaC) in the connecting tubule and blocked by benzamil. High salt intake reduces Af-Art vasoconstrictor ability in Dahl salt-sensitive rats (Dahl SS). Previously, we measured CTGF indirectly, by differences between TGF responses with and without CTGF inhibition. We recently developed a new method to measure CTGF more directly by simultaneously inhibiting NKCC2 and the Na+/H+ exchanger (NHE). We hypothesize that in vivo during simultaneous inhibition of NKCC2 and NHE, CTGF causes an Af-Art dilatation revealed by an increase in stop-flow pressure (PSF) in Dahl SS and that is enhanced with a high salt intake. In the presence of furosemide alone, increasing nephron perfusion did not change the PSF in either Dahl salt-resistant rats (Dahl SR) or Dahl SS. When furosemide and an NHE inhibitor, dimethylamiloride, were perfused simultaneously, an increase in tubular flow caused Af-Art dilatation that was demonstrated by an increase in PSF. This increase was greater in Dahl SS [4.5 ± 0.4 (SE) mmHg] than in Dahl SR (2.5 ± 0.3 mmHg; P < 0.01). We confirmed that CTGF causes this vasodilation, since benzamil completely blocked this effect. However, a high salt intake did not augment the Af-Art dilatation. We conclude that during simultaneous inhibition of NKCC2 and NHE in the nephron, CTGF induces Af-Art dilatation and a high salt intake failed to enhance this effect.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Arteríolas
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Circulação Renal
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Vasodilatação
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Cloreto de Sódio na Dieta
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Glomérulos Renais
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Túbulos Renais
Limite:
Animals
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article