OXIDATIVE STRESS IN THE DAHL HYPERTENSIVE RAT

Enhanced production of oxygen free radicals may play a role in hyperte nsion by affecting vascular smooth muscle contraction, resistance to b lood flow, and organ damage. The aim of this study was to determine wh ether oxygen free radicals are involved in the development of salt-ind uced hypertension. Dahl salt-sensitive (Dahl-S) and salt-resistant (Da hl-R) rats were fed either a high salt (6.0% NaCl) or low salt (0.3% N aCl) diet for 4 weeks. The high salt diet caused the development of se vere hypertension in Dahl-S animals and had no effect on blood pressur e in Dahl-R animals. A tetranitroblue tetrazolium dye was used to dete ct superoxide radicals in microvessels of the mesentery. Light absorpt ion measurements revealed enhanced staining along the endothelium of a rterioles and venules in hypertensive Dahl-S animals, with significant ly lower values in normotensive animals. in addition, a Clark electroc hemical electrode was used to measure hydrogen peroxide levels in fres h plasma. Hypertensive Dahl-S animals had a higher plasma hydrogen per oxide concentration compared with their normotensive counterparts (2.8 1+/-0.43 versus 2.10+/-0.41 mu mol/L), while no difference was detecte d between high- and low salt-treated Dahl-R animals (1.70+/-0.35 versu s 1.56+/-0.51 mu mol/L). The plasma hydrogen peroxide levels of all gr oups correlated with mean arterial pressure (r=.77). These findings de monstrate an enhanced production of oxygen free radicals in the microv asculature of hypertensive Dahl-S rats.