title: [Effects of ascorbic acid on relaxation of ex vivo Bufo gastrocnemius during sustained isometric contraction].
abstract: OBJECTIVE
  To investigate the effect of ascorbic acid (VC) on relaxation of ex vivo Bufo gastrocnemius during sustained isometric contraction.
  
  
  METHODS
  Dynamic tension of the muscle was recorded under constant voltage stimulation within 7.0 min at 2 s intervals. The rest tension and relaxation rate of the muscle was obtained by weighted fitting to the relaxation process of tension <90% of its peak with a mono-exponential model to characterize the muscular relaxation.
  
  
  RESULTS
  VC at 2.0 mmol/L alone or in combination with the inhibitors of the antixoidation enzymes (surperoxide dismutase, glutathione peroxidase and catalase) resulted in negligible alterations in the muscular relaxation kinetics. VC combined with the inhibitor of surperoxide dismutase resulted in significantly lowered relaxation rate while increased rest tension, but VC with the inhibitor of either catalase or glutathione peroxidase showed negligible action. VC combined with the inhibitors of all the 3 enzymes also caused significant effect on the muscular relaxation kinetics, which was similar the effect of VC with superoxide dismutase inhibitor.
  
  
  CONCLUSIONS
  VC at high concentration may result in oxidative toxicity to the biological system rich in transitional metal ion complexes but with low antioxidation capacity by causing superoxide-mediated oxidative damages.
authors.affiliation: Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology, College of Pharmaceutical Sciences, Chongqing Medical University, Chongqing, China.
authors.forename: Sheng-bing
authors.initials: SB
authors.lastname: Li
authors.forename: Rui
authors.initials: R
authors.lastname: Guo
authors.forename: Fei
authors.initials: F
authors.lastname: Liao
authors.forename: Yu-ping
authors.initials: YP
authors.lastname: Zuo
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.forename: An-ping
authors.initials: AP
authors.lastname: Sun
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D002025:Bufonidae; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology
chemical_list: D001205:Ascorbic Acid