Effect of dietary NaCl on norepinephrine turnover in the Dahl rat

To evaluate neural mechanisms in salt-sensitive hypertension, norepinephrine turnover rates were measured in peripheral tissues and selected brain areas of Dahl salt-sensitive and salt-resistant rats receiving either 1% or 7% NaCl diets for 5 weeks. Norepinephrine turnover was determined by measuring tissue norepinephrine in untreated animals or in separate groups killed 2, 4, 6, and 10 hours after alpha-methyl-tyrosine. Plasma volume (radiolabeled albumin) was also measured. Arterial pressure of Dahl S rats receiving 7% NaCl (167 +/- 4 mm Hg) was higher (p less than 0.001) than that of Dahl S rats receiving 1% NaCl (141 +/- 3mm Hg), which was higher (p less than 0.001) than that of Dahl R rats receiving both NaCl intakes. Norepinephrine turnover was increased (p less than 0.01) by 7% NaCl in both heart and brown adipose tissue in Dahl S rats, whereas norepinephrine turnover in Dahl R rats was decreased (p less than 0.01) by the 7% NaCl intake in the heart and kidney. On the high NaCl intake, norepinephrine turnover in heart and adipose tissue was lower (p less than 0.05) in Dahl R rats than in Dahl S rats. In brain stem tissue, with the 1% NaCl diet, norepinephrine turnover was higher (p less than 0.001) in Dahl S rats than in Dahl R rats, and norepinephrine turnover was inhibited (p less than 0.001) by the high NaCl intake in Dahl S rats but not in Dahl R rats. In posterior hypothalamus, norepinephrine turnover was inhibited (p less than 0.01) by the high NaCl intake in Dahl R rats but not in Dahl S rats.(ABSTRACT TRUNCATED AT 250 WORDS)