Insulin antagonism in cultured rat myoblasts secondary to chronic exposure to insulin

Rat myoblasts grown in culture for 5 days responded acutely to insulin (10 mU/ml) over a 3 hour incubation period by stimulating C14-glucose incorporation into glycogen by 260%. When these cells were grown in the presence of insulin (10 mU/ml) for the first 4 days (no exposure to insulin during the final 24 hours), insulin had no significant acute effect. These data provide direct evidence that insulation itself may induce antagonism under certain conditions.