The effects of growth hormone and insulin-like growth factors I and II on glutamine metabolism by skeletal muscle of the rat in vitro.

Soleus muscle preparations of the rat were incubated in the presence of growth hormone, IGF-I or IGF-II. Growth hormone (10 and 100 ng/ml) increased, but IGF-I and IGF-II were without effect on the concentration of glutamine in soleus muscle. Growth hormone was without effect on the rate of release of glutamine from muscle. In contrast, the rate of release of glutamine was decreased in the presence of IGF-I (750 ng/ml) and increased in the presence of IGF-II (250 and 750 ng/ml). Growth hormone and the IGFs may therefore play an important role in the control of glutamine metabolism by skeletal muscle.