Abstract
These studies were designed to analyze the factors which induced compensatory hypertrophy of muscle in normal and alloxan diabetic rats and to compare the differences between the mechanism of hypertrophy and insulin action. Compensatory hypertrophy was induced in the rat plantaris and soleus muscles on one limb by ipsilateral tenotomy of the synergistic muscle, the gastrocnemius.
Experimental results were as follows;
1) In normal rats, the wet weight of gastrocnemius of the operated limb was 18.5% smaller and that of the plantaris and soleus was 17% and 24% greater, respectively, than their controls after 7 days of operation.
The gain of the dry weight of these hypertrophied muscles was directly proportional to that of the wet weight. Inspite of the gain of weight, the water content of hypertrophied muscles was about 80% of the wet weight.
In alloxan diabetic rats, the rate and extent of muscle hypertrophy of the plantaris and soleus were almost similar to that of normal rats.
Moreover, work induced hypertrophy of skeletal muscle occurred independently of developmental growth and insulin action.
2) The accumulation of α-aminoisobutyric acid-14C (α-AIB-14C) by the gastrocnemius, plantaris and soleus of normal rats was studied in vivo after ispilateral tenotomy of the gastrocnemius. Simultaneously, the extra-cellular space of each muscle was determined as inulin-3H space.
The hypertrophied muscles, the plantaris and soleus of operated limb, significantly concentrated α-AIB-14C than the contralateral controls within 3 to 5 days after operation.
On the other hand, the atrophied muscle, the gastrocnemius, concentrated α-AIB-14C to lesser extent than the contralateral control, but statistically insignificant.
The extra-cellular space of operated gastrocnemius did not diminish and that of ipsilateral plantaris and soleus increased in its volume at 3 to 5 days after the tenotomy of gastrocnemius.
