title: Exercise-induced brachial artery vasodilation: role of free radicals.
abstract: Originally thought of as simply damaging or toxic "accidents" of in vivo chemistry, free radicals are becoming increasingly recognized as redox signaling molecules implicit in cellular homeostasis. Indeed, at the vascular level, it is plausible that oxidative stress plays a regulatory role in normal vascular function. Using electron paramagnetic resonance (EPR) spectroscopy, we sought to document the ability of an oral antioxidant cocktail (vitamins C, E, and alpha-lipoic acid) to reduce circulating free radicals, and we employed Doppler ultrasound to examine the consequence of an antioxidant-mediated reduction in oxidative stress on exercise-induced vasodilation. A total of 25 young (18-31 yr) healthy male subjects partook in these studies. EPR spectroscopy revealed a reduction in circulating free radicals following antioxidant administration at rest ( approximately 98%) and as a consequence of exercise ( approximately 85%). Plasma total antioxidant capacity and vitamin C both increased following the ingestion of the antioxidant cocktail, whereas vitamin E levels were not influenced by the ingestion of the antioxidants. Brachial artery vasodilation during submaximal forearm handgrip exercise was greater with the placebo (7.4 +/- 1.8%) than with the antioxidant cocktail (2.3 +/- 0.7%). These data document the efficacy of an oral antioxidant cocktail in reducing free radicals and suggest that, in a healthy state, the aggressive disruption of the delicate balance between pro- and antioxidant forces can negatively impact vascular function. These findings implicate an exercise-induced reliance upon pro-oxidant-stimulated vasodilation, thereby revealing an important and positive vascular role for free radicals.
authors.affiliation: Dept of Medicine, Physiology Division, Univ of California San Diego, La Jolla, CA 92093-0623, USA. rrichardson@ucsd.edu
authors.forename: Russell S
authors.initials: RS
authors.lastname: Richardson
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Donato
authors.forename: Abhimanyu
authors.initials: A
authors.lastname: Uberoi
authors.forename: D Walter
authors.initials: DW
authors.lastname: Wray
authors.forename: Lesley
authors.initials: L
authors.lastname: Lawrenson
authors.forename: Steven
authors.initials: S
authors.lastname: Nishiyama
authors.forename: Damian M
authors.initials: DM
authors.lastname: Bailey
mesh_terms: D000293:Adolescent; D000328:Adult; D000975:Antioxidants / Q000378:metabolism* / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000097:blood; D001783:Blood Flow Velocity / Q000187:drug effects; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D004578:Electron Spin Resonance Spectroscopy; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005542:Forearm / Q000098:blood supply; D005609:Free Radicals / Q000378:metabolism; D018737:Hand Strength; D006801:Humans; D008297:Male; D018384:Oxidative Stress; D012016:Reference Values; D018608:Ultrasonography, Doppler; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014810:Vitamin E / Q000097:blood
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D014810:Vitamin E; D001205:Ascorbic Acid