Nitric Oxide Regulates Renin Release During Salt Depletion but Does Not Alter Angiotensin Responses in Normal Humans

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Abstract
Background: Animal studies suggest that nitric oxide regulates the renin-angiotensin- aldosterone system, but this effect varies among species. The effects of nitric oxide on the renin-angiotensin-aldosterone system in humans were assessed using L-nitrosomonomethyl arginine (L-NMMA), an antagonist of nitric oxide synthase. Methods and Results: In experiment 1, subjects were pretreated with furosemide to induce salt depletion and received placebo-controlled infusions of L-NMMA followed by measure ments of plasma renin activity. In experiment 2, subjects were given angiotensin I and II intravenously with and without L-NMMA to assess the effects of nitric oxide on systemic pressor and aldosterone responses. In experiment 3, brachial arterial infusions of angio tensin I and II were given with and without L-NMMA, and forearm blood flow was mea sured to assess the effects of nitric oxide on vascular responses to the angiotensin peptides. During salt depletion, L-NMMA infusion resulted in significantly higher plasma renin activ ity. L-NMMA had no effect on systemic or forearm pressor responses or aldosterone responses to angiotensin I and II infusions. Conclusions: These results indicate that nitric oxide regulates the renin response to salt depletion in healthy humans but does not affect responses to angiotensin.