Fibre number and sizes of mouse soleus muscle in early postnatal protein malnutrition.

The effect of early postnatal protein malnutrition on the development of soleus muscle was investigated in 26 mice (13 males, 13 females). The control group received a balanced diet containing 18% lactalbumin while the protein-malnourished group received protein deficient diet containing 0.5% lactalbumin. The body weight was determined both at 3 weeks (weaning age) and 12 weeks of age. The soleus muscle weight, total number and sizes of muscle fibres were also determined at 12 weeks of age for each mouse. There was considerable retardation of body weight and soleus muscle weight. The smaller soleus muscle of protein-malnourished mice resulted from loss of muscle fibres and hypotrophy of the remaining fibres. Permanent retardation of body weight after recovery from early postnatal protein malnutrition may be as a result of loss of muscle fibres during that period.