Angiotensin II and nitric oxide: a question of balance

The vasoconstrictor peptide angiotensin II (Ang II) and the endogenous vasodilator nitric oxide (NO) have many antagonistic effects, as well as influencing each other's production and functioning. In the short-term, Ang II stimulates NO release, thus modulating the vasoconstrictor actions of the peptide. In the long-term, Ang II influences the expression of all three NO synthase (NOS) isoforms, while NO downregulates the Ang II Type I (AT1) receptor, contributing to the protective role of NO in the vasculature. Within the cardiovascular system, Ang II and NO also have antagonistic effects on vascular remodeling and apoptosis. In the kidney, the distribution of the NOS isoforms coincides with the sites of the components of the renin-angiotensin system. NO influences renin secretion from the kidney, and NO-Ang II interactions are important in the control of glomerular and tubular function. In the adrenal gland, NO has been shown to affect Ang II-induced aldosterone synthesis, while in the brain NO appears to influence Ang II-induced drinking behavior, although conflicting data have been reported. In this review, we focus on the diverse ways in which Ang II and NO interact, and on the importance of maintaining a balance between these two important mediators.