Abstract 11611: Muscle Superoxide Dismutase and Augmented Autonomic Responsiveness in Rats With Peripheral Artery Disease

Abstract

Background: During exercise, responses of sympathetic nerve and blood pressure are amplified in patients with peripheral artery disease (PAD). This worsens the restricted blood flow directed to the limbs in this disease. The purpose of this study was to determine the role played by muscle oxidative stress in regulating the augmented autonomic responses to static exercise in PAD. Superoxide dismutases (SOD) is a class of enzymes to catalyze the dismutation of superoxide into oxygen and hydrogen peroxide, and considered as an important antioxidant. Thus, our specific hypothesis was that limb ischemia impairs muscle SOD and thereby leads to abnormal autonomic responsiveness observed in PAD. Methods and Results: We used a rat model of femoral artery ligation to study PAD. Note that all data are presented as mean ± SE. First, western blot analysis shows that 72 hours of femoral occlusion significantly decreased the protein levels of SOD in the oxidative muscle (optical density: 1.02±0.03 in control vs. 0.21±0.02 after ligation, P< 0.05; n = 6 in each group) and glycolytic muscle (optical density: 1.03±0.03 in control vs. 0.65±0.04 after ligation, P< 0.05; n = 6 in each group). Additional immunofluorescence study demonstrates down-regulation of SOD in the ischemic hindlimb muscles. Second, the reflex blood pressure response to static muscle contraction was examined in control rats (n=5) and rats with 72 hours of femoral occlusion (n=6). The data show that the augmented reflex pressor response to muscle contraction was significantly attenuated after compensating SOD in ischemic muscles by chronic administration of tempol (a mimetic of SOD, 30 mg over a period of 72 hours) into the hindlimb. In the ligated rats, mean arterial pressure response was 26±3 mmHg with no tempol (n=6) and 12±2 mmHg with tempol application ( P< 0.05 vs. group with no tempol; n =5). Conclusions: Muscle SOD is blunted in the ischemic limbs and supplement of SOD mimetic for anti-oxidation improves the augmented blood pressure response during static exercise, which is beneficial to the restricted blood flow to the limbs in PAD patients.