Effect of dietary sodium intake on the expression of endothelin-converting enzyme in the renal medulla.
OBJECTIVE
Endothelin-converting enzyme (ECE) catalyzes the generation of endothelin-1 (ET-1) from its inactive precursor big-ET-1. Previous studies suggested that the ET-1 system is involved in the regulation of sodium excretion by the kidney. In particular, ET-1 via the ET(B) receptor-mediated signaling has been shown to increase renal medullary blood flow and decrease sodium transport in the collecting duct, both acting to promote renal sodium excretion. The present study was designed to evaluate the possibility that alterations in dietary salt intake may regulate the ECE-1.


METHODS
Wistar rats were fed for 3 days either with a diet containing low salt (0.01% NaCl), normal salt (0.5% NaCl), or high salt intake, either by high salt diet (4% NaCl) or normal salt diet plus 0.9% saline drinking. The expression of and immunoreactive protein levels of ECE-1 in the renal medulla was studied by RT-PCR, Northern blotting and Western blotting techniques.


RESULTS
The expression of ECE-1 mRNA (by RT-PCR and Northern blotting), as well as the immunoreactive levels of ECE-1, were significantly higher in the renal medulla of rats exposed to high salt intake than in rats on normal salt diet.


CONCLUSIONS
The findings suggest that upregulation of ECE-1, leading to increased generation of ET-1 in the renal medulla, may be a compensatory mechanism promoting enhanced sodium excretion by the kidney in response to high salt intake.
Fattal
I
I
Department of Physiology and Biophysics, Faculty of Medicine and the Rappaport Family Institute for Research in Medical Sciences, Technion, IIT, Haifa, Israel.
Abassi
Z
Z
Ovcharenko
E
E
Shimada
K
K
Takahashi
M
M
Hoffman
A
A
Winaver
J
J
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D000072396:Endothelin-Converting Enzymes; D015870:Gene Expression / Q000187:drug effects; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000097:blood / Q000652:urine; D012982:Sodium, Dietary / Q000494:pharmacology*; D015854:Up-Regulation
D012982:Sodium, Dietary; D012964:Sodium; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes