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First published online on November 14, 2003.
 Copyright © 2003 by The Physiological Society
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Received October 13, 2003
Revised November 10, 2003
Accepted after revision November 14, 2003

{beta}2-Agonist administration reverses muscle wasting and improves muscle function in aged rats

James G Ryall1, David R Plant1, Paul Gregorevic1, Martin N Sillence2, and Gordon S Lynch1*

1 University of Melbourne
2 Charles Sturt University

* To whom correspondence should be addressed. E-mail: gsl{at}unimelb.edu.au.

The {beta}2-adrenoceptor agonist ({beta} 2-agonist), fenoterol, has potent anabolic effects on rat skeletal muscle. We conducted an extensive dose-response study to determine the most efficacious dose of fenoterol for increasing skeletal muscle mass in adult rats and used this dose in testing the hypothesis that fenoterol may have therapeutic potential for ameliorating age-related muscle wasting and weakness. We used adult (16 month old) rats that had completed their growth and development, and old (28 month old) rats that exhibited characteristic muscle wasting and weakness, and treated them daily with either fenoterol (1.4 mg/kg, i.p), or saline vehicle, for four weeks. Following treatment, functional characteristics of fast-twitch extensor digitorum longus (EDL) and predominantly slow-twitch soleus muscles of the hindlimb were assessed in vitro. Untreated old rats exhibited a loss of skeletal muscle mass and a decrease in force producing capacity, in both fast and slow muscles, compared with adult rats (P < 0.05). However, there was no age-associated decrease in skeletal muscle {beta}- adrenoceptor density, nor was the muscle response to chronic {beta}-agonist stimulation reduced with age. Thus, muscle mass and force producing capacity of EDL and soleus muscles from old rats treated with fenoterol was equivalent to, or greater than, untreated adult rats. The increase in mass and strength was attributed to a non-selective increase in the cross-sectional area of all muscle fibre types, in both the EDL and soleus. Fenoterol treatment caused a small increase in fatiguability due to a decrease in oxidative metabolism in both EDL and soleus muscles, with some cardiac hypertrophy. Further studies are needed to fully separate the desirable effects on skeletal muscle and the undesirable effects on the heart. Nevertheless, our results demonstrate that fenoterol is a powerful anabolic agent that can restore muscle mass and strength in old rats, and provide preliminary evidence of therapeutic potential for age-related muscle wasting and weakness.


Key words: Ageing • B-adrenoceptor • Skeletal muscle




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