Background: Endothelial nitric oxide synthase (eNOS) is known to be expressed
in endothelium and smooth muscle cells of arteries. The aim of this study was to investigate
the expression of eNOS in intimal and medial layer of aorta from rats fed with a high salt diet
and its modulation by losartan and tempol.
Methods: Rats were fed during three weeks with: normal salt diet (NS, 0.4% NaCl); high salt
diet (HS, 8% NaCl); NS plus tempol 1 mM (NS-T); HS plus tempol (HS-T); NS plus losartan
40mg.kg-1 (NS-L) and HS plus losartan (HS-L). Systolic blood pressure was recorded by the
tail cuff method. Rats were then anaesthetized and the thoracic aorta and small arteries (bronchial
branches of aorta) were processed to evaluate the expression of eNOS and aquaporin-1
(AQP-1) by immunohistochemistry.
Results: HS group showed increased systolic blood pressure, increased eNOS and AQP-1
immunoexpression in the aorta intimal layer, and decreased eNOS immunoexpression in the
aorta medial layer, respect to NS group. Losartan and tempol prevented hypertension and
changes in the expression of eNOS and AQP-1 of the intimal layer. However, only tempol increased
the expression of eNOS elicited by sodium overload in the medial layer of the aorta
and small arteries respect to HS group.
Conclusion: A high salt diet decreases eNOS expression in vascular smooth muscle layers of
aorta and small arteries, which is reversed by tempol. These results suggest an adverse effect
of oxidative stress on vascular eNOS in rats fed a high salt diet independently of hypertension.