Insulin effects in denervated and non-weight-bearing rat soleus muscle.

Previous reports indicated that glucose uptake in denervated muscle is resistant to insulin, while in non-weight-bearing (unweighted) muscle this effect of insulin is enhanced. To extend the comparison of these differences, insulin effects on amino acid uptake and protein metabolism were studied in soleus muscles subjected to denervation or unweighting. Denervated muscle showed insulin resistance of both 2-deoxy[1,2-3H]glucose and alpha-[methyl-3H]aminoisobutyric acid uptake whereas unweighted muscle showed an increased or normal response, respectively. Atrophy was greater in denervated than in unweighted muscle, apparently due to faster protein degradation. The stimulation of protein synthesis and the inhibition of protein degradation by insulin was generally less in denervated than in unweighted muscle. Since metabolic measurements in denervated-unweighted muscles did not differ from those in denervated-weight-bearing muscles, effects of denervation must be independent of leg posture.