AJP - Renal Physiology, Vol 260, Issue 6 890-F897, Copyright © 1991 by American Physiological Society
High-NaCl diets increase natriuretic and diuretic responses in salt-resistant but not salt-sensitive SHR
M. S. Mozaffari, S. Jirakulsomchok, Z. H. Shao and J. M. Wyss
Department of Cell Biology, University of Alabama, Birmingham 35294.
This study tested the hypothesis that NaCl-sensitive spontaneously
hypertensive rats (SHR-S) display a defect in natriuretic and diuretic
responses to acute volume loading that contributes to the rise in arterial
pressure observed when the rats are fed a high-NaCl diet. Seven-week-old
SHR-S and NaCl-resistant SHR rats (SHR-R) and normotensive (Wistar-Kyoto
and Sprague-Dawley rats) were fed high- or basal NaCl diets. After 2.5 wk
on the diets, preinstrumented conscious rats received an intravenous
infusion (5% body wt; 0.5 ml/min) of isotonic saline, and urine was
collected through a bladder catheter for 90 min. Control rats on the
high-NaCl diet (compared with basal) excreted a significantly greater
percentage of Na+ and volume load. In contrast, SHR-S on high-NaCl diet
(compared with basal) had a very small increase in natriuretic response and
no increase in diuretic response to volume expansion. The effect of renal
denervation on natriuretic and diuretic responses to volume load was
tested. In SHR-R on 1 and 8% NaCl diets, renal denervation had little or no
effect on these responses, suggesting that renal nerves do not play a
prominent role in the dietary NaCl-induced increases in the natriuretic and
diuretic responses to volume load. These results demonstrate that
NaCl-resistant rats rapidly adapt to diets high in NaCl content with
increased natriuretic and diuretic responses to acute volume loading. The
failure of SHR-S to adapt to the dietary challenge may result in volume
loading and a secondary increase in arterial pressure after feeding.
