Reactive oxygen species have emerged as important molecules in cardiovascular dysfunction such as diabetes and hypertension. Recent work has shown that oxidative stress and angiotensin II signaling mutually regulate each other by multiple mechanisms and contribute to the development of hypertension. The present study was carried out to investigate the role of renal AT1 receptor signaling in oxidative-stress mediated hypertension. Male Sprague-Dawley rats received tap water (control) or 30 mM L-buthionine sulfoximine (BSO), an oxidant, with and without 1 mM tempol (an antioxidant) for 2 weeks. Compared with control rats, BSO-treated rats exhibited increased oxidative stress and reduced antioxidants levels and developed hypertension. BSO treatment also caused increased renal proximal tubular AT1 receptor protein abundance, message levels and ligand binding. In these rats, angiotensin II caused significantly higher accumulation of inositol trisphosphate (IP3) and phospholipase C (PLC) activation which was sensitive to blockade by AT1 but not to AT2 antagonist. Also, angiotensin II-mediated, AT1 dependent, MAP kinase, Na/K-ATPase and Na/H-exchanger 3 activation was higher in BSO-treated rats than in control rats. Tempol supplementation of BSO-treated rats restored redox status, normalized AT1 receptor expression and decreased blood pressure. Tempol also normalized the angiotensin II-mediated, AT1 dependent, IP3 accumulation and PLC, MAP kinase, Na/K-ATPase and Na/H-exchanger 3 stimulation. These data suggest that oxidative stress leads to AT1 receptor upregulation, which in turn causes overstimulation of sodium transporters and subsequently contribute to sodium retention and hypertension. Tempol, while reducing oxidative stress, normalizes AT1 receptor signaling and decreases blood pressure.