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Am J Physiol Renal Physiol (May 27, 2009). doi:10.1152/ajprenal.90729.2008
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Submitted on December 4, 2008
Revised on May 20, 2009
Accepted on May 20, 2009

Inhibition of Natriuretic Factors Increases Blood Pressure in Rats

Anees Ahmad Banday1* and Mustafa F Lokhandwala1

1 University of Houston

* To whom correspondence should be addressed. E-mail: abanday{at}uh.edu.

Renal dopamine and nitric oxide contribute to natriuresis during high salt intake which maintains sodium and blood pressure homeostasis. We wanted to determine whether concurrent inhibition of these natriuretic factors increase blood pressure during high sodium intake. Male Sprague Dawley rats were divided into the following groups: 1) vehicle (V)-tap water, 2) NaCl-1% NaCl drinking water, 3) BSO-30 mM L-buthionine sulfoximine, an oxidant, 4) BSO plus NaCl, 5) BSO plus NaCl with 1 mM tempol (antioxidant). Compared to vehicle, NaCl intake for 10 days doubled sodium intake and increased urinary dopamine level but reduced urinary nitric oxide content. NaCl intake also reduced basal renal proximal tubular Na/K-ATPase activity with no effect on blood pressure. However, NaCl intake in BSO-treated rats failed to reduce basal Na/K-ATPase activity despite higher urinary dopamine levels. Also, dopamine failed to inhibit proximal tubular Na/K-ATPase activity and these rats exhibited reduced urinary nitric oxide levels and high blood pressure. Tempol supplementation in NaCl plus BSO-treated rats reduced blood pressure. BSO treatment alone did not affect the urinary nitric oxide and dopamine levels or blood pressure. However, dopamine failed to inhibit proximal tubular Na/K-ATPase activity in BSO-treated rats. BSO treatment also increased basal protein kinase C activity, D1 receptor serine phosphorylation and oxidative markers like malondialdehyde and 8-isoprostane. We suggest that NaCl -mediated reduction in nitric oxide does not increase blood pressure due to activation of D1 receptor signaling. Conversely, oxidative stress provoked inhibition of D1 receptor signaling fails to elevate blood pressure due to presence of normal nitric oxide. However, simultaneously decreasing nitric oxide levels with NaCl and inhibiting D1 receptor signaling with BSO elevated blood pressure.







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