Abstract 530: Renal Vasoconstriction is Augmented during Exercise in Peripheral Arterial Disease Patients: Contributions of Muscle Mechanoreflex and Oxidative Stress

Abstract

Peripheral arterial disease (PAD) patients have augmented blood pressure increases during exercise. It is unknown whether PAD patients have greater renal vasoconstriction during exercise and how much the muscle mechanoreflex or oxidative stress contribute to this response. Eleven PAD patients and 10 healthy controls (CON) performed 4 minutes of mild, rhythmic, plantarflexion exercise of increasing intensity (0.5-2kg) with each leg (most and least affected legs for PAD). Eight PAD patients also performed exercise with their most affected leg during intravenous, high-dose, ascorbic acid (AA) infusion. Renal blood flow velocity (RBFV; Doppler ultrasound), mean arterial blood pressure (MAP; Finometer), and heart rate (HR; ECG) were measured. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as MAP/RBFV. Statistical analysis involved repeated measures ANOVA and paired samples t -tests. Baseline RVR and MAP were similar while HR was higher in PAD compared to CON (RVR: 2.08±0.23 vs. 1.87±0.20 arbitrary units, MAP: 94±3 vs. 93±3 mmHg, and HR: 72±3 vs. 59±3 b.min -1 (p<0.05) for PAD and CON, respectively). PAD had greater RVR increases from baseline during exercise with both the most and least affected legs compared to CON, specifically during the first minute of exercise (PAD most: 2.08±0.23 to 2.60±0.29 (+26±5%) and PAD least: 1.96±0.24 to 2.22±0.25 (+17±5%) vs. CON: 1.87±0.20 to 1.91±0.20 (+3±3%) for the first minute of exercise, both p <0.05). AA infusion did not alter baseline RVR, MAP or HR. AA attenuated the augmented RVR increase in PAD during the first minute of exercise with the most affected leg (PAD most without AA: 2.10±0.31 to 2.78±0.38 (+33±2%) vs. PAD most with AA: 1.88±0.26 to 2.23±0.26 (+21±2%) for the first minute of exercise, p <0.05). In conclusion, these findings suggest that PAD patients have augmented renal vasoconstriction during exercise, with the muscle mechanoreflex and oxidative stress contributing to this increased response.