Changes of ribosomal capacity for protein synthesis, contraction and histochemical properties of muscle after implantation of fast nerve into denervated and into self-reinnervated slow soleus muscle of the rat.

The ribosomal capacity for protein synthesis in the fast extensor digitorum longus muscle of the rat is markedly higher than in the slow soleus muscle. Implantation of the "fast" peroneal nerve into the denervated or into the self-reinnervated soleus muscle results in transformation (increase) of capacity of isolated ribosomes for protein synthesis into that of the fast muscle type. The degree of transformation is higher after implantation into the self-reinnervated than into the denervated soleus muscle. A high degree of recovery of weight and tetanic tension output is recorded after the "fast" nerve implantation. The effect of transformation with respect to contraction properties is considerably more marked in the case of heteroinnervation of the denervated muscle and persists even after 5 months of heteroinnervation. Transformation of the histochemical muscle fibre pattern is also more pronounced after heteroinnervation of the denervated than self-reinnervated soleus muscle; the muscle acquires the fibre pattern of the fast extensor digitorum longus muscle. The acquisition of the reciprocal pattern of oxidative and glycolytic enzymes suggests that the activation of protein synthesis induced by the foreign "fast" nerve supply is coupled with the operation of specific RNA species.