Objective: To determine if oxygen free radicals derived from xanthine oxida
se are involved in the development of salt-induced hypertension. Enhanced p
roduction of oxygen free radicals may play a role in hypertension by affect
ing vascular smooth muscle contraction and provide a mechanism for lesion f
ormation.
Methods: Dahl salt-sensitive (Dahl-S) and salt-resistant (Dahl-R) rats mere
fed either a low-salt, high-salt or high-salt + tungsten diet for 4 wk. In
vivo production of superoxide (O-2(-)) was detected by the reduction of a
tetranitroblue tetrazolium (TNBT) dye in the rat mesentery, while plasma hy
drogen peroxide (H2O2) production levels mere determined using a modified e
lectrochemical electrode technique.
Results: The tungsten diet lowered the blood pressure of Dahl-S rats compar
ed to high-salt-treated Dahl-S rats, but had no effect on blood pressure in
Dahl-R rats. Light absorption of formazan deposits revealed that tungsten-
treated Dahl-S rats had reduced TNBT staining along the endothelium of arte
rioles and venules compared to hypertensive, high-salt-treated Dahl-S rats.
In addition, tungsten-treated Dahl-S rats had a lower plasma H2O2 concentr
ation compared to hypertensive, high-salt-treated Dahl-S rats.
Conclusions: These findings indicate that xanthine oxidase-derived oxygen f
ree radicals are involved in the pathogenesis of salt-induced hypertension.