Permissive effect of ATP on insulin-stimulated sugar transport by rat soleus muscle.

The stimulatory effect of insulin (0.1 U/ml) on D-xylose uptake was progressively lost when rat soleus muscles were preincubated at 37 degrees C under anaerobic conditions for longer than 30 min; after 90 min these muscles were completely insensitive to insulin. This effect was associated with the loss of muscle ATP. When the breakdown of ATP was retarded either by lowering the preincubation temperature or by preincubation with 5 mM glucose, the effect of insulin in anaerobic muscle was correspondingly prolonged. Under certain conditions, externally added ATP promoted an effect of insulin in otherwise insulin-unresponsive muscles. This effect was small in magnitude and was complicated by the degradation of the added ATP in the incubation medium and by the fact that ATP also tended to inhibit insulin-stimulated xylose uptake. These results indicate that there is a relationship between insulin-stimulated sugar transport and muscle ATP levels. This supports the proposal that there may be some ATP-dependent reaction(s) involved in the mechanism whereby insulin promotes the process of muscle sugar transport.