Effects of NaCl on vascular responsiveness in male rats.

The effect of chronic salt treatment on systolic blood pressure and vascular adrenergic responsiveness was studied in rats. Vascular reactivity of aortic smooth muscle to potassium chloride and sodium nitrite was similar in both groups, indicating that salt treatment did not alter the regular contraction and relaxation process of the smooth muscle. Isoproterenol-induced relaxation was similar for both treated and control groups demonstrating that salt treatment had no effect on vascular beta-adrenergic responsiveness. However, when aortic smooth muscle was incubated with angiotensin II or norepinephrine, a significant increase in responsiveness was observed in the aortic smooth muscle of the salt-treated group compared to the control group. Collectively, these results suggest that salt, per se, does not affect systolic blood pressure or peripheral beta-adrenergic responsiveness, but does result in a significantly enhanced alpha-adrenergic responsiveness. The implication of these results for experimental hypertension are discussed.