Chronic long-term electrostimulation creates a unique metabolic enzyme profile in rabbit fast-twitch muscle

Long-term low-frequency stimulation (up to 120 days) of rabbit fast-twitch tibialis anterior muscle led, in a first-order-like time course, to changes in enzyme activities of energy metabolism which became stable with ongoing stimulation after 50 days. The glycolytic enzymes decreased to 30-40% of their normal values, but remained 2-3-fold higher than in heart or soleus muscle. The LDH isozyme pattern ultimately resembled that of the slow-twitch soleus muscle. Citrate synthase activity increased 3.7-fold which brought this enzyme to a value 45% above that of heart. These results indicate that chronic stimulation does not simply convert the fast-twitch muscle into a soleus-like slow-twitch muscle, but creates a tissue of unique metabolic properties.