title: Failure of oxygen radical scavengers to modify fatigue in electrically stimulated muscle.
abstract: We used in situ gastrocnemius muscle of anaesthetized dogs to test the hypothesis that O2 radical production during muscle contraction contributes to fatigue. Muscle tension was measured with a force transducer and blood flow was monitored with an electromagnetic flow probe. Muscle contractions were produced by stimulating the nerve for 15 min at 20 Hz, 12 trains/min, and a duty cycle of 0.25. Three groups of seven animals were given an infusion of 0.2 mL.min-1 of either saline, low-dose oxygen radical scavengers (250 IU.mL-1 superoxide dismutase, 640 IU.mL-1 polyethylene glycol (PEG)-catalase, 0.25 mg.mL-1 deferoxamine, and 0.1 mg.mL-1 oxypurinol), or high-dose oxygen radical scavengers (3300 IU.mL-1 superoxide dismutase, 6600 IU.mL-1 PEG-catalase, 2.5 mg.mL-1 deferoxamine, and 0.1 mg.mL-1 oxypurinol). Blood flow and vascular resistance of the gastrocnemius muscle during stimulation did not differ among groups. After 15 min of stimulation, the developed tension (represented as a percentage of initial tension developed) was 66 +/- 7% in the saline treated group, 70 +/- 6% in the low-dose group, and 70 +/- 4% in the high-dose group. The change in tension during recovery was not significant in the control or low-dose groups. However, there was partial recovery in the high-dose group. In conclusion, in this preparation, oxygen radical scavengers did not delay the development of decreased muscle tension.
authors.affiliation: Department of Medicine, Royal Victoria Hospital, Montréal, Qué., Canada.
authors.forename: I
authors.initials: I
authors.lastname: Shrier
authors.forename: S
authors.initials: S
authors.lastname: Hussain
authors.forename: S
authors.initials: S
authors.lastname: Magder
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D004285:Dogs; D004558:Electric Stimulation; D005221:Fatigue / Q000503:physiopathology*; D016166:Free Radical Scavengers; D006614:Hindlimb / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000187:drug effects* / Q000503:physiopathology; D010100:Oxygen / Q000494:pharmacology*; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D016166:Free Radical Scavengers; D002245:Carbon Dioxide; D010100:Oxygen