Oxidative stress contributes to vascular endothelial dysfunction in heart failure

Congestive heart failure (HF) is characterized by inadequate nitric oxide (NO) production in the vasculature. Because NO is degraded by oxygen radicals, we hypothesized that NO is degraded faster in HF from inadequate peripheral arterial antioxidant reserves. HF was induced in male Sprague-Dawley rats by left coronary artery ligation. Vascular endothelial function was evaluated by measuring the NO-mediated vasorelaxation response to acetylcholine (ACh; 10^-9-10^-4 M) in excised aortas. This was repeated with the free radical generator pyrogallol (20μM) and again with pyrogallol and superoxide dismutase (SOD; 60U/ml). Aortic and myocardial SOD activity was also determined. ACh-induced vasorelaxation was reduced in HF (n=9) compared with normal control rats (n=11; P<0.001). Pyrogallol further reduced vasorelaxation in HF: 74±11% at 10^-4 M ACh versus 58 ± 10% in normal control rats (P<0.004). There was a trend (P=0.06) toward reduced SOD activity in HF aortas. In conclusion, altered NO-dependent vasorelaxation in HF is in part due to excessive degradation of NO and is likely related to reduced vascular SOD activity.