Low salt intake down-regulates the guanylin signaling pathway in rat distal colon.
OBJECTIVE
Guanylin, an endogenous gastrointestinal peptide, causes the translocation of NaCl from interstitial fluid to the intestinal lumen. The aim of this study was to examine whether changes in dietary salt intake lead to compensatory changes in expression of the guanylin signaling pathway.


METHODS
Rats received low-, normal-, or high-sodium diets for 1 week. Colonic guanylin expression was evaluated by Western and Northern blotting, rates of guanylin secretion by measuring biologically active guanylin released into the medium from colon explants, and expression of the guanylin receptor (C-type guanylate cyclase) by Northern blotting and bioassay.


RESULTS
By every criterion, the low-salt diet reduced expression of guanylin to 30%-40% of the level found in control animals. Guanylin receptor expression was also decreased, although less dramatically and with a lower statistical significance. For both guanylin and guanylin receptor, the high-salt diet had no significant effect on expression.


CONCLUSIONS
The data support the hypothesis that the guanylin pathway is down-regulated as an adaptive response to salt restriction.
Li
Z
Z
Department of Physiology, University of North Carolina, Chapel Hill, USA. zpll@med.unc.edu
Knowles
J W
JW
Goyeau
D
D
Prabhakar
S
S
Short
D B
DB
Perkins
A G
AG
Goy
M F
MF
D000818:Animals; D003106:Colon / Q000378:metabolism*; D015536:Down-Regulation; D005768:Gastrointestinal Hormones; D008297:Male; D045265:Natriuretic Peptides; D010455:Peptides / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
D005768:Gastrointestinal Hormones; D045265:Natriuretic Peptides; D010455:Peptides; D017673:Sodium Chloride, Dietary; C072685:guanylin