Coordinate regulation of renal expression of nitric oxide synthase,
renin, and angiotensinogen mrna by dietary salt.
Singh, Inderjit, Morgan Grams, Wei-Hua Wang, Tianxin Yang, Paul
Killen, Ann Smart, Jurgen Schnermann, and Josie P. Briggs.
Departments of Physiology and Internal Medicine, The University of
Michigan, Ann Arbor, Michigan 48104
APStracts 3:0015F, 1996.
Experiments were performed to examine the effect of changes in dietary
salt intake on neuronal nitric oxide synthase (ncNOS), renin and
angiotensinogen mRNA expression in the kidney. Three groups of
Sprague Dawley rats were studied: rats maintained on a 3 % Na diet
plus 0.45% NaCl in the drinking fluid for 7 days (high salt), rats
given a single injection of furosemide (2 mg/kg ip) and a 0.03% Na
diet for 7 days (low salt), and rats on a diet containing 0.2 % Na
(control). mRNA expression was assessed with RT-PCR methods using
cDNA prepared from samples of renal cortex and microdissected tubular
segments. ncNOS PCR products were quantified by comparison with a
dilution series of a mutant deletion template. Compared to their
respective control, ncNOS mRNA levels in renal cortical tissue were
elevated in rats on a low salt diet and reduced in rats on a high
salt diet. Similar changes were seen in the expression of renin and
angiotensinogen mRNA. Dietary salt intake did not alter the mRNA
levels for ncNOS from the inner medulla, or for ecNOS and iNOS in the
renal cortex. ncNOS mRNA was found in glomeruli dissected with the
macula densa containing segment (MDCS), but only at marginal levels
in glomeruli without MDCS. Furthermore, a low salt diet stimulated
ncNOS mRNA in glomeruli with MDCS 6.2 fold compared to a high salt
diet. There was no effect of salt diet on ncNOS mRNA in glomeruli
without MDCS, or in inner medullary collecting ducts. These results
suggest that ncNOS expression in macula densa cells is inversely
regulated by salt intake, thus following the known response of the
renin-angiotensin system to changes in salt balance.
Received 2 August 1995; accepted in final form 3 January 1996.
APS Manuscript Number F253-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 January 96