Work-induced muscle hypertrophy in vitamin D-deficient rats

To determine if vitamin D deficiency would retard the ability of muscle to hypertrophy in response to mechanical stress, we severed the gastrocnemius tendon on one leg of rats in each of three groups, the treatment of which differed only in the amount of vitamin D in the diet. After 1 week the increased size of the soleus and plantaris in the leg in which the gastrocnemius was severed relative to that of the sham operated leg, was determined for each rat. Despite differences in body weight and serum calcium among the groups, we found no difference in the percent of muscle hypertrophy. We conclude that muscle hypertrophy can occur in response to local mechanical forces despite a deficient hormonal environment that otherwise retards growth.