AJP - Endocrinology and Metabolism, Vol 272, Issue 5 E941-E944, Copyright © 1997 by American Physiological Society
Clenbuterol increases the expression of myogenin but not myoD in immobilized rat muscles
M. I. Delday and C. A. Maltin
Rowett Research Institute, Bucksburn, Aberdeen, United Kingdom.
Immobilization of one hindlimb of young rats in plantar flexion for 3 days
led to changes in the plantaris muscles. These comprised a loss of muscle
mass and a reduction in protein and RNA content, but no change in the
transcript levels of the myogenic regulatory factors myogenin and myoD.
Dietary administration of the beta-adrenoceptor agonist clenbuterol (2
mg/kg diet), which has been shown to ameliorate muscle wasting in a wide
range of atrophic conditions, also limited muscle wasting in terms of
weight, protein, and RNA in the immobilized plantaris muscles. In addition,
drug treatment in immobilized plantaris muscles was associated with a
marked increase in the steady-state levels of mRNA for myogenin
(approximately 360% increase over control) but not myoD. These data provide
the first evidence for independent changes in these two myogenic regulatory
factors in immobilized muscle and suggest that the action of clenbuterol on
these factors may depend on the mechanistic basis for the atrophic
response.
