title: Effect of vitamin C on hyperoxia-induced vasoconstriction in exercising skeletal muscle.
abstract: Hyperoxia can cause substantial reductions in peripheral and coronary blood flow at rest and during exercise, which may be caused by reactive oxygen species (ROS) generated during hyperoxia. The aim of this study was to investigate the role of ROS in hyperoxia-induced reductions in skeletal muscle blood flow during forearm exercise. We hypothesized that infusion of vitamin C would abolish the effects of hyperoxia on the forearm blood flow (FBF) responses to exercise. Twelve young healthy adults performed rhythmic forearm handgrip exercise (10% of maximum voluntary contraction for 5 min) during normoxia and hyperoxia. For each condition, two trials were conducted with intra-arterial administration of saline or vitamin C. FBF was measured using Doppler ultrasound. During hyperoxia with saline, FBF and forearm vascular conductance (FVC) were 86.3 ± 5.1 and 86.8 ± 5.2%, respectively, of the normoxic values (100%) (P < 0.05). During vitamin C, hyperoxic FBF and FVC responses were 90.9 ± 4.2 and 90.9 ± 4.1%, respectively, of the normoxic values (P = 0.57 and 0.59). Subjects were then divided into three subgroups based on their percent decrease in FBF (>20, 10-20, and <10%) during hyperoxia. In the subgroup that demonstrated the greatest hyperoxia-induced changes (>20%), FBF and FVC during hyperoxia were 67.1 ± 4.0 and 66.8 ± 3.6%, respectively, of the normoxic values. Vitamin C abolished these effects on FBF and FVC with values that were 102.0 ± 5.2 and 100.8 ± 6.1%, respectively. However, vitamin C had no effect in the other two subgroups. This analysis is consistent with the idea that ROS generation blunts the FBF responses to exercise in the subjects most affected by hyperoxia.
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Ranadive.Sushant@mayo.edu.
authors.forename: Sushant M
authors.initials: SM
authors.lastname: Ranadive
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Joyner
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and.
authors.forename: Branton G
authors.initials: BG
authors.lastname: Walker
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Taylor
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Darren P
authors.initials: DP
authors.lastname: Casey
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage*; D001205:Ascorbic Acid / Q000008:administration & dosage*; D001783:Blood Flow Velocity; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000503:physiopathology; D015444:Exercise; D005260:Female; D005542:Forearm; D018737:Hand Strength; D006801:Humans; D018496:Hyperoxia / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D007261:Infusions, Intra-Arterial; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012039:Regional Blood Flow; D013997:Time Factors; D018616:Ultrasonography, Doppler, Duplex; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D001205:Ascorbic Acid
keywords: ascorbic acid; forearm blood flow; vascular conductance