Muscle changes in protein-deprived young rats. A morphometrical, histochemical and ultrastructural study

Rats were reared on a standard diet up to the age of 6 weeks when they were divided into two groups. One was fed on a diet containing 14% protein and the other on a diet with only 1.5% protein. The size of the various fibre types of the EDL muscle of both groups was assessed at 6 and 25 weeks of age. All the fibre types of protein-deprived rats were smaller compared to the age-matched controls, the difference being most evident in the 2B fibres. In the protein-deprived rats the 2B fibres atrophied while the type 1 and type 2A fibres simply failed to grow. Histochemical and ultrastructural examination revealed a marked reduction of the subsarcolemmal mitochondria after prolonged protein deprivation; normally large accumulations of mitochondria are seen preferentially in type 2A fibres.