The effects of amylin on carbohydrate metabolism in skeletal muscle in vitro and in vivo.

1. The effects of synthetic human amylin on basal and insulin-stimulated (100 and 1000 microunits/ml) rates of lactate formation, glucose oxidation and glycogen synthesis were measured in the isolated rat soleus muscle preparation incubated in the presence of various concentrations of glucose (5, 11 and 22 mM). 2. The rate of glucose utilization was increased by about 2-fold by increasing the glucose concentration from 5 to 22 mM. 3. Synthetic human amylin (10 nM) significantly inhibited (by 46-56%) glycogen synthesis, irrespective of the concentration of insulin or glucose present in the incubation medium. 4. Amylin (10 nM) did not affect insulin-stimulated rates of 2-deoxy[3H]glucose transport and phosphorylation. 5. Intraperitoneal administration of insulin (100 micrograms/kg) to rats in vivo stimulated the rate of [U-14C]glucose incorporation into glycogen in the diaphragm by about 80-fold. This rate was decreased (by 28%) by co-administration of amylin (66 micrograms/kg).