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Publication AbstractsClenbuterol Attenuates Muscle Atrophy and Dysfunction in Hindlimb-Suspended RatsStephen L. Dodd and Thomas J. KoestererAviat Space Environ Med 2002; 73:635-9 AbstractBackground: Muscle wasting and dysfunction is a significant problem in prolonged exposure to microgravity. Hypothesis: This study tested the hypothesis that a beta-adrenergic agonist (clenbuterol) could attenuate the effects of 14 d of unweighting on mixed fiber type skeletal muscle. Methods: Female, Sprague-Dawley rats were maintained in cages as: 1. controls (C; n = 12); 2. hindlimb suspended via tail casting (HLU; n = 12); 3. clenbuterol injected daily (3 mg · kg-1) (CL; n = 10); or 4. hindlimb suspended and injected with clenbuterol daily (3 mg · kg-1) (HLU + CL; n = 12). Results: At the end of the study, both CL and HLU + CL had higher body weights compared with HLU (p < 0.05). Gastrocnemius mass (wet weight and muscle weight/body weight) and maximal tetanic force were significantly decreased during HLU (p < 0.05) (mean ± SE; mass: C = 1.6 ± 0.04 g, HLU = 1.2 ± 0.05 g; force: C = 3483 ± 113 g, HLU = 2765 ± 52 g). Clenbuterol attenuated the decrease in both mass and force generation (mass: HLU + CL = 1.4 ± 0.04 g; force: HLU + CL = 3162 ± 135). Twitch tension during HLU (1057 ± 72 g) was significantly less (p < 0.05) than during C (1362 ± 61 g), and clenbuterol did not attenuate this loss. HLU caused a decrease (p < 0.05) in force at 30 Hz and decreased one-half relaxation time (½ RT) (p < 0.05) from 30 ± 2 to 25 ± 2 ms. Clenbuterol caused further decreases (p < 0.05) in both force (20 and 30 Hz) and ½ RT. Conclusions: These data suggest that a beta-adrenergic agonist may be of benefit in attenuating wasting and the reduced maximal force seen during periods of unweighting in mixed fiber type muscle.Keywords: hindlimb-unweighting, muscle mass, contractile properties. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 73, Number 7 of the ASME journal.
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