Intravenous ascorbic acid does not block the pressor or sympathetic nerve response to ischemic fatiguing rhythmic handgrip exercise

Abstract

Reactive oxygen species stimulate group IV muscle afferents in rats but the effects of oxidative stress on the exercise pressor reflex in humans is unknown. The purpose of the current study was to determine the effect of intravenous ascorbic acid (Vitamin C) on the exercise pressor reflex in humans. Seven young healthy nonsmokers participated in the current study, which was part of a large protocol in our laboratory. On Day 1, they underwent systemic infusions of saline and then Vitamin C; on Day 2, they underwent a saline time/volume control. Muscle sympathetic nerve activity (MSNA), heart rate, and blood pressure were monitored throughout baseline, ischemic fatiguing rhythmic handgrip exercise, and post‐handgrip circulatory arrest. The change in mean arterial pressure from baseline to fatigue was not different between saline (Δ 35±6 mmHg) and Vitamin C (Δ 31±6 mmHg). Similarly, heart rate (Δ 22±4 bpm vs Δ 26±4 bpm) and MSNA burst rate (Δ 22±6 bpm vs Δ 22±5bpm) were also not different between treatments. Metaboreflex activation and time control experiments similarly showed no treatment effects. The current data suggest that oxidative stress does not contribute to the magnitude of blood pressure or MSNA response seen during fatiguing handgrip in young healthy subjects.This study supported by P01 HL096570 (LIS) and UL1 RR033184 (LIS)