Control of renin release by dietary NaCl in the rat

The purpose of the present study is to determine whether changes of plasma renin activity (PRA) induced by dietary NaCl are mediated by a renal tubular mechanism or by a neural mechanism. Male Sprague-Dawley rats were placed on low-, normal-, or high-NaCl diets for 1 wk (n = 8 for each group). There were no group differences of glomerular filtration rate (GFR), renal plasma flow, Na+ or Cl- delivery to the loop, Na+ or Cl- reabsorption in the loop, Na+ or Cl- concentration in early distal tubular fluid, or Na+ or Cl- delivery to the early distal tubule. PRA of rats on normal NaCl (4.8 ng.ml-1.h-1 +/- 0.8) was greater (P less than 0.05) than that of rats on high NaCl (3.3 +/- 0.4) and less (P less than 0.05) than that of animals on low NaCl (9.1 +/- 1.8). To determine whether alterations of PRA by dietary NaCl might be related to low-pressure baroreceptors with vagal afferents, animals were bilaterally vagotomized after micropuncture. Forty-five minutes after vagotomy, PRA increased (P less than 0.05) on each of the diets, however, after vagotomy mean PRA in animals fed normal (10.9 +/- 1.8) and low NaCl (13.2 +/- 2.2) did not differ. Thus our results do not support the hypothesis that suppression of PRA by dietary NaCl loading is related to a renal tubular mechanism. A vagally mediated mechanism may contribute to renin suppression by dietary NaCl.