Effect of work-induced hypertrophy on skeletal muscle of tumor- and nontumor-bearing rats.

Synergistic muscles (soleus and plantaris) from a gastrocnemius-tenotomized hindlimb were compared to the same muscles in a sham-operated hindlimb in both tumor-bearing and non tumor-bearing rats. In nontumor-bearing animals muscle from the tenotomized hindlimb had a significant increase in wet weight (26%), percent-water (5%), and total nitrogen/muscle (10%) consistent with muscular hypertrophy. In tumor-bearing animals, muscle from the tenotomized hindlimb had a significant increase in wet weight and percent water, but there was no significant difference in total nitrogen/muscle. As the tumor burden increased, the final muscle weight, in both the tenotomized and sham-operated hindlimb, was found to decrease proportionately. Only in animals with large (23% body wt) tumor burdens did hypertrophied muscle weigh significantly less than sham-operated muscle from nontumor-bearing animals. This indicated that, in rats with large tumor burdens, work-induced hypertrophy was unable to preserve muscle mass despite the fact that hypertrophied muscle was 24% heavier than contralateral sham-operated muscle.