Alteration of the maximal activity of the gluconeogenetic enzyme fructose-1,6-diphosphatase of skeletal muscle by cross-reinnervation. A histochemical and biochemical investigation of fatiguability-related aspects.

Fatiguability is a determining characteristic of different muscle fibre types. An important aspect, indirectly related to fatiguability, gluconeogenesis, was investigated by observing fructose-1,6-diphosphatase (FDP) activity in experimental models prepared in rabbits by cross-reinnervation of the fatigue-resistant m.soleus (postural muscle) and the highly fatiguable m.flexor digitorum longus (fast muscle -- m.fdl). The resultant reprogramming of the m. soleus was associated with greatly intensified FDP activity. Changes in the m.fdl 6-9 months after cross-reinnervation indicated a shift in the opposite direction. The study adds some data on the much neglected state of fatiguability to the otherwise much explored field of alien reinnervation.