Effects of acute and chronic hindlimb suspension on sensitivity and responsiveness to insulin in the rat soleus muscle.

The effects of acute (24 h) and chronic (5 weeks) hindlimb suspension on insulin-stimulated glucose utilization by the rat soleus muscle were studied in vitro. Hindlimb suspension resulted in an enhancement of basal glucose transport, lactate production, and glycogen synthesis. An increase in the sensitivity of these processes to insulin occurred as early as 24 h and persisted for 5 weeks of the muscle unloading. An increased responsiveness to insulin was found only for glucose transport after 24 h. The present data do not support the concept that the enhanced glucose utilization and improved muscle insulin sensitivity during hindlimb suspension are related to muscle atrophy, which is not observed in the early stage of muscle unweighting.