Acute ascorbic acid and hindlimb skeletal muscle blood flow distribution in old rats: rest and exercise

Abstract

Excess reactive oxygen species are implicated in the impaired peripheral vascular function evident during exercise in older individuals. We tested the hypothesis that an acute infusion of the antioxidant ascorbic acid (AA) in old rats would improve antioxidant capacity and reduce oxidative stress and, therefore, elevate hindlimb muscle blood flow at rest and during treadmill exercise in muscles containing principally type I and IIa muscle fibers. Total and individual hindlimb skeletal muscle blood flow was measured (radiolabeled microspheres) in old rats (26-28 months) at rest (n = 8) and during treadmill exercise (n = 8; 20 m·min⁻¹, 5% grade) before and after AA treatment (76 mg·(kg body mass)⁻¹ intra-arterial (i.a.) injection). AA elevated total antioxidant capacity (rest, ~37%; and exercise, 31%) and reduced oxidative stress (~26%, exercise only). AA reduced resting total hindlimb muscle blood flow (control, 25 ± 3; AA, 16 ± 2 mL·min⁻¹·(100 g)⁻¹; p < 0.05) and blood flow to 8 of 28 individual muscles with no fiber-type correlation (p > 0.05). During exercise there was no effect of AA on total hindlimb muscle blood flow (control, 154 ± 14; AA, 162 ± 13 mL·min⁻¹·(100 g)⁻¹; p > 0.05) or blood flow to any individual muscle. This disconnect between whole-body antioxidant status and skeletal muscle blood flow in old rats mandates consideration when pursuing antioxidant treatments experimentally or clinically in older populations.

Modulation of Endothelial Glycocalyx and Microcirculation in Healthy Young Men during High-Intensity Sprint Interval Cycling-Exercise by Supplementation with Pomegranate Extract. A Randomized Controlled Trial

“…Animal studies in young rat spinotrapezius muscle showed that acute antioxidant supplementation significantly reduced skeletal muscle blood flow both at rest and during contractions [48], possibly resulting in increased lactate production. Animal models have revealed that high dosages of antioxidant supplements could shut down specific redox-sensitive cell-signaling pathways and accordingly reduce the synthesis of new muscle mitochondria and endogenous antioxidant production [43], leading to impaired lactate clearance and oxidation [49].…”