Effect of the beta 2-adrenergic agonist clenbuterol on the growth of fast- and slow-twitch skeletal muscle of the dystrophic (C57BL6J dy2J/dy2J) mouse.

Clenbuterol (4mg/kg in diet for 21 days) had no statistically significant effect on whole body growth. It did cause a significant increase (18.2%) in wet weight of the fast twitch muscle extensor digitorum longus (EDL) and a corresponding 14.9% increase in total muscle protein. In transverse sections through dystrophic muscle fibre sizes were more variable than in normal muscle. Clenbuterol treatment resulted in a reduction in the proportion of small diameter fibres, and therefore an increase in mean fibre diameter, in dystrophic EDL. Clenbuterol had no significant effect upon the slow twitch muscle soleus.